For example, before the mall event where your identity it's revealed, you can go to train, if you fight on the sewers against the Minyiaks, depending on your choices, you'll get 1 or 2 power and skill points, that applies to some future fights too
There's no penalty for doing that. All checks so far require sufficient power OR skill, so as long you keep up on skill, you can forego the power gains from corruption.