Complete the game in Campaign.

Complete the game with every secret and speed chips to get General Corrosive as a playable character in multi-player only.

Collect the following number of secret chips while in the campaign mode to access the corresponding multi-player arena.

Corrosive City: 110 secret chips
DMA Death Sphere: 40 secret chips
Mac mines: 138 secret chips
Matt's Big Gun Fun: 8 secret chips
Morbot Land: 15 secret chips
Ruins: 60 secret chips
The Coliseum: 85 secret chips
The Reactor Factor: 25 secret chips
The Trenches: 4 secret chips