Corruptive refers to a play style in Super Smash Bros. 4 that Mario (and by extension, Dr. Mario) amiibo could adopt and utilize in tournament play. It takes advantage of Mario’s unique AI to “ruin” its opponents’ play style to gain the upper hand in battle.
Corruptive trainers teach their Mario amiibo to overuse its side special, grabs, and aerial attacks. In a tournament setting, each set consists of three games. In the first game, the Mario amiibo will lose. In the second match, the Mario amiibo essentially “transfers” its poor training to its opponent; it can then win the second and third matches to win the entire set. Corruptive amiibo were rather unpopular in tournaments; many trainers considered it unfair that a purposefully poorly-trained character could defeat a well-trained one with relative ease.
In Super Smash Bros. Ultimate, a corruptive playstyle can still exist, but to a much lesser extent. With the advent of the Learn button, amiibo can become immune to corruption by switching their Learn button off. As a result, corruptive characters are hardly mentioned, as most amiibo are sent to tournaments with Learning off.