Overpowered abilities, attacks, moves, perks, etc. that have made a game too easy

[patronmacabre]

The Demolition Boost order in Valkyria Chronicles. It allows your shocktroopers to kill tanks. When I convince someone to play that game (which I think is fantastic and one of my favorite games), I specifically avoid telling them about how that order, because it removes all the challenge (and, I think, a lot of the tension) from the game.