noun
power creep
Wasei-eigo term used in gaming, anime, and manga communities to describe the gradual increase in character or item power over time, often making older content obsolete.
wasei-eigo (Japanese-coined English), from power infla(tion)
このゲームはパワーインフレが激しくて、昔のキャラがすぐ使えなくなる。
This game has severe power creep, so old characters quickly become unusable.
パワーインフレを抑えるために、運営はバランス調整を入れた。
To curb power creep, the developers implemented balance adjustments.