Empire Earth/YMMV

Game Breaker:
- The Sniper Rush (investing heavily in expensive snipers early on in a modern age game and using them en masse to instantly kill enemy units in hordes) act like this.
- Towers are also incredibly powerful and almost unstoppable except for otherwise fragile siege units and massing them can provide an impressive defense.
- There is no friendly fire in this game. There are, however, nuclear weapons. Say hello to saving your armed forces from direct assault by nuking them, leaving your enemies destroyed and your forces strangely unscathed.
Ruined FOREVER: Many fans of the first Empire Earth said this about EEII.
- And many more fans from the first two to EEIII.
Sequelitis: Kicked in for the third one.
That One Level: The second scenario in the Russian Campaign in the first game. Very few people were able to beat that without using a trick to create a duplicate of the scenario and activating the ability to cheat in it.
- The second scenario in the Asian campaign is even worse, as you have to complete a long list of highly failable objectives on a tight resource budget while assailed by unlimited enemy reinforcements. At one point your citizens rebel and to make them stop you have to delete part of your military. Saving a region from economic collapse is hard.