Victor Gains Loser's Powers

Sometimes characters get stronger by leveling up. Other times they have to train under hard conditions to take a level in Badass. But there are times the character only needs to defeat his opponent and he'll get a boost to his strength, getting this way powers related to his enemy. There are some ways this can happen:
 * The character has an ability that lets him copy the powers of anyone he defeats. He doesn't need to kill his opponent (though that's what usually happens); just defeating his enemy will grant him any power his opponent had. He doesn't steal the power outright; he merely copies it.
 * The character learns an ability or special move (normally one exact to one his opponent had) after the match, or he may get an object that lets him use or learn the technique.
 * The character obtains a special weapon after the match. It can't be any common weapon: it must be a unique weapon, and sometimes the carriers are famous for carrying it. The weapon reflects the defeated opponent in some way, be it the same weapon he used or one that reflects the battle style among other things.

Subtrope of Power Copying. Compare with You Will Be Assimilated, where no defeat is needed because the enemy is made part of the character directly, and Power Parasite, where the power getting involves the original user can't use them anymore. See Your Soul Is Mine for one way this kind of thing can come about.

Anime & Manga

 * Kakuzu from Naruto has survived by taking the hearts of his defeated opponents, allowing him to use said opponents chakra type.
 * From Naruto too, Bee has acquired Samehada after his previous owner was killed.
 * The titular character of Inuyasha wields the Tessaiga, a sword whose explicit power is to absorb the essence (and thus, the abilities) of the enemies it slays. Enemy throws an impregnable barrier? Kill the enemy, and the Tessaiga can break through barriers. Enemy turns to diamond and flings spears of the material? Kill it, and Tessaiga can turn to diamond and shoot off diamond spears. Enemy can slice open a rift into the world of the dead? And so on and so forth. Furthermore, these are not inherent abilities; Inuyasha deliberately switches them on and off, triggering the appropriate transformation on the blade's appearance.
 * Yu-Gi-Oh! has a creature called Diabound, which absorbs the powers of every creature it destroys,.
 * In Digimon Tamers, Beelzemon could use the techniques of the Digimon he'd absorbed in battle. This becomes a problem when he performs.
 * In Digimon Xros Wars, several of the Bagra generals can absorb members of their armies to gain their powers. The first general to do so is MadLeomon.
 * The victorious mechs in Gigantic Formula gain abilities, technology and personnel from the countries they defeat.

Film

 * The Highlander films featured this, as an immortal would gain the power and skill of any other immortals they beheaded.

Live-Action TV

 * In Charmed, Warlocks are supposed to have the ability to steal the powers of any supernatural beings they kill. However, they never actually did this very much, and this attribute of theirs was mostly just used as their motivation for trying to kill the main characters. The only Warlock character who actually went around stealing abilities was a single-episode Monster of the Week. Season 7's Big Bad, Zankou, also had the ability to absorb the powers of those he killed, but he only used it once, in his introductory episode.
 * Applies to Highlander the Series. To quote Joe Dawson in the opening narration "The winner takes his enemy's head, and with it, his power." Although it's not as pronounced as some of the other examples, immortals do sometimes pick up traits or skills after a quickening.

Video Games

 * Every single Mega Man except Trigger follows this trope to certain extents, some in unique ways.
 * The Classic series seems to have it as an innate ability of top end robots, since Mega Man, Proto Man, and Bass can all use the weapons of defeated Robot Masters. In Power Fighters, Duo can too. Roll has only been shown to use Robot Master weapons, and only in the non-canon Marvel vs. Capcom series. (Furthermore, its successor Tatsunoko vs. Capcom ditched this aspect in her new moveset.)
 * EXE has his Souls/Cross/etc. It had this as well in the form of chips.
 * More Details: Souls and Crosses fit into this trope solely on the level of a gameplay mechanic. In-universe, Souls and Crosses are manifestations of The Power of Friendship. Souls occur when MegaMan and whichever of his companions at the moment experience a strong moment of empathy; Crosses, however, occur when Lan earns access to various other NetNavis by successfully completing various tests posed by the respective Operators (each of which involves Lan assuming control of that particular Netnavi). Notably, each Test occurs as a "class", which suggests that Link Navis are not necessarily exclusive relationships.
 * More Details 2: Battle Chips are various weaponry that may be used freely by NetNavis, many of which consist of an enemy's attack or ability, and are derived by defeating the corresponding virus or NetNavi. There were originally only the distinctions of standard chips and Navi Chips (the latter being limited), but the third game introduced the Standard - Mega (Navi Chips and those of equivalent power) - Giga (basically Finishing Move chips and fifth-level Navi Chips) classification that would last on through Mega Man Star Force. Battle Chips will only appear if the enemy is taken out efficiently - the leftover data stagnates as time passes, and Standard and Navi Chips may change code or even power level, respectively. (Of course, for collection purposes, this may be sometimes necessary).
 * In ZX and ZX Advent, Grey and Ashe go the extra mile and completely copy the forms of bosses.
 * The Star Force series has this in the form of Mega Cards that are gained from defeating bosses and regular enemies.
 * The Card Force in Star Force is largely a simplification of the Battle Network system, such as removing chip codes to make streamlining easier. Many of the same rules apply.
 * Zero often simply learns a new fighting move mimicking the boss.
 * Certain skills may be learned by doing particularly well at a boss battle. The Z-Knuckle in 4, on the other hand will actually rip an enemy's weapon out of their hand and/or body.
 * Samus in Metroid Fusion had all her abilities copied by X. After killing X-infected bosses (which tend to be able to produce similar attacks), she can absorb the X-parasite to regain that power.
 * Metroid Prime 2 does something similar, where, after losing most of her starting abilities to a mob of Ing, she has to regain them in one-on-one boss battles where they're used against her.
 * In Zero Mission, Samus somehow gets the Charge Beam this way, even though her opponent, Deorem (A.K.A the "Charge Beam Beast"), never used anything like it. Metroid Prime also has a few examples, such as the Varia Suit from Flaaghra, the Spider Ball from Thardus, and the Phazon Suit from the Omega Pirate. Metroid Prime 3 has Samus gain the Ice Missiles, Plasma Beam, Grapple Voltage, and all the Phazon upgrades this way.
 * In Metroid Prime 3, fighting the other Hunters that got corrupted nets her a new ability closely related to them.
 * Soma Cruz from Castlevania Aria of Sorrow and Dawn of Sorrow can equip the abilities of monsters by defeating them and absorbing their souls. It is revealed in the former that . Now, never displayed this ability until it was retconned in by  in Portrait of Ruin, but it's been described as a variation of.
 * In Pokémon you can get the bosses' powers--in a sense. Most Gym Leaders' final Pokémon either have a move they shouldn't learn by leveling up, or have a move that is just really easy to spam. When you beat them, they usually give you a TM of it.
 * Emerl from Sonic Battle gets one random skill card from each character in the battle after every battle in which it participates in Story Mode. The cards allow Emerl to use fighting moves from the other characters.
 * Many spells in Puzzle Quest: Challenge of the Warlords can be learnt by the player by capturing the monster that uses them (by solving a puzzle) and then learnt in the citadel (by means of a special game mode). A few spells can also be accessed by capturing a mount. However, in all cases, the player has higher mana costs than the monster that normally uses them (or the class that learns them normally).
 * In Metal Gear Solid 4 Guns of the Patriots, Snake gains an ability from the defeated members of the BB Corps.
 * In Metal Gear Solid 3 Snake Eater, the yet-to-be Big Boss could acquire the bosses camouflage suits (except The End's) by dropping their stamina to zero instead of their health, along with The End's special weapon, the tranquilizer sniper gun Mosin Nagant.
 * Just to be clear: you can get the end's camo, but you have to Hold up the End by pointing a gun at his head so he refuses you 3 times, then he gives it up. Could be seen as defeating the end in terms of stealth.
 * The Sega Genesis Shmup Gaiares let the player "capture" an enemy's weapon and use it, though the captured weapon didn't always look the same as when the enemy used it.
 * Kingdom Hearts does it somewhat subtly. Strike Raid, Ars Arcanum, Ragnarok, and Sonic Blade all come straight from the movepool of the boss you just beat. But they do have different names, and their executions are slightly adapted to fit the powers of the Keyblade.
 * Devil May Cry has been an embodiment of this trope in the third and fourth games. Dante can claim the powers of slain boss enemies after the fight. Whereas in DMC 3 it seems to happen almost as an afterthought in Dante's case, in DMC 4 Nero is shown intentionally 'harvesting' these powers after every boss he defeats, since he could ostensibly leave the shiny orbs on their pedestals (or not, as you HAVE to have the things on the pedestals to advance).
 * Dragon Age Origins has a portion of the Broken Circle quest that plays like a massive homage to Mega Man. The hero must defeat (or aid) 5 individuals to gain their powers, then use said powers to track down and defeat a sub-boss for each of the 5 areas. The end-boss of the sequence completes the Mega Man homage with a Boss Rush consisting of all the previous sub-bosses before you can fight his "true form".
 * In Shadow Hearts: Covenant, Yuri can gain stronger fusions. To do that he must defeat monsters in the real world to gain their souls and then sacrifice those to the appropriate elemental gravestone. Then he has to fight an incarnate of the fusion spirit before he can use it. In the case of his more powerful fusions, this amounts to beating a god and stealing its power.
 * Quistis Trepe from Final Fantasy VIII can learn the abilities of some enemies by using an special object they drop after they're defeated.
 * The fan-made game called Mega Mari (based on Marisa Kirisame of Touhou) plays with this notion: the game is a "clone" of Mega Man 2 (with massively jacked up difficulty) which involves Marisa (or her friend Alice) defeating eight bosses, stealing their weapons in the process, before gaining access to Patchouli's castle/library so Marisa can steal some more books from the poor asthmatic sorceress.
 * In regular canon, most of Marisa's spells are stolen from previous opponents although she has no explicit spell-copying ability. Fighting people just gives her ideas.
 * Ace Combat Zero has you acquire some planes in this fashion. As in, shoot down a named ace squadron flying a particular type of plane, and it's yours to buy.
 * Guild Wars has a skill called Signet of Capture that lets you capture a skill from a defeated boss. This is one of two ways to learn elite skills, and the only way to learn a skill you haven't unlocked on your account.
 * Kratos in God of War tends to do this to his enemies, in one of two ways. Either he'll steal the weapon straight out of the enemy's hands (and beat them to death with it) or he'll cut the enemy to pieces and use one of their body parts as a weapon. For example, taking off a Gorgon's head and using it as a petrifying ray gun on his enemies, or stealing the wings of Icarus from the man himself as he's flying.
 * Scaler from, well, Scaler, has the ability to transform into other lizard-y creatures by defeating a specific amount of that particular creature.
 * In Rune Factory 3, you can upgrade staves with boss drops, which then allows you to use that boss's special attack. They tend not to be too practical, though, as they use a prohibitively large amount of RP.
 * In Kongai, the Gem of Souls enables its possessor to absorb the innate ability of any opponent the character kills.
 * One very neat feature in the mostly-shitty fighting game Blood Storm was that defeating an opponent would grant you their signature ability.

Web Comics

 * Yuuki from Sparkling Generation Valkyrie Yuuki is able to steal power Although technically she didnt beat them and take their powers she just took their powers.
 * Princess Ip, the apparent greatest enemy of Princess Pi, can steal the powers of whoever she kills.

Web Original

 * In the sixth season of Red vs. Blue, Reconstruction, the new Big Bad known as the Meta steals AI and Armor Enhancements from the bodies of Freelancers that he's killed.

Western Animation

 * The series' ultimate evil, Vilgax, gets this ability himself when he's reintroduced in the later seasons of Ben 10 Alien Force, using it to absorb the powers of the galaxy's greatest heroes after he beats them and takes over their planets. While he uses a machine to do that he can only claim the enemies powers after he's defeated them in combat.