In a time where the most powerful decks were four-life decks, Radical Beam
If your Benched Pokmon have any damage counters on them, this attack does 100 more damage
Then the next opponent in turn order (or, if it's an opponent's turn, the opponent whose turn it is) chooses a card in hand and sets it aside without revealing it
His unpredictable nature translates well to gameplay, creating moments where he can flip the board or vanish entirely
Whenever you cast a spell with power, toughness, or loyalty equal to the chosen number, target artifact or creature becomes an artifact creature with base power and toughness X/X until end of turn, where X is the chosen number
The more important reason Gaddock was contained was that green wasn't a natural fit for the decks that wanted Gaddock, or in some cases green was but white wasn't, and his legendary status made it difficult to go too far out of the way to get him