Here is the full list of all 26 Rival Megagun trophies - there are 5 bronze, 15 silver, 5 gold and 1 platinum.
Collect all trophies.
Collect all cards.
Complete Arcade mode on Very Hard with no retries.
Fire 500 special attacks.
Transform into your Mega Gunship 100 times.
Complete Arcade mode on Hard with no retries.
Equip a special weapon.
Achieve the Host's Hero Ending in Arcade mode.
Chain 100 enemies.
Complete Arcade mode on Normal with no retries.
Achieve Smith's Hero Ending in Arcade mode.
Achieve Buddy 2.0's Hero Ending in Arcade mode.
Achieve Ruby's Hero Ending in Arcade mode.
Achieve Nano's Hero Ending in Arcade mode.
Achieve Dr. Magic's Hero Ending in Arcade mode.
Simultaneously launch an attack charged to 200%, transform into your Mega Gunship, and spawn at least 25 drones.
Achieve Gen's Hero Ending in Arcade mode.
Complete Arcade mode on Easy with no retries.
Break Harvester Core's shell using Mega Gunship.
Defeat the Host in arcade mode with no retries.
Clear the portal stage in arcade mode with no retries.
Equip 2 gears.
Complete the tutorial.
Play 1000 versus matches.
Play 500 versus matches.
Play 100 versus matches.