Here is the full list of all 51 Knockout City trophies - there are 37 bronze, 12 silver, 1 gold and 1 platinum.
Unlock all other Trophies
Score 1000 KO Assists
Travel 100km in ballform
Complete 100 Daily Contracts
Win 10 rounds with five times the opponent's score
Catch 1000 dodgeballs
Win a match while having a Legendary Outfit equipped
KO two opponents with a single Bomb ball
Earn 250,000 XP
Score 3 Hits with a Multi Ball in quick succession
Win matches with 10 unique Outfits
Win matches with 20 Outfit and/or Glove Styles
Score 1000 KOs
Score 10 KOs without being KO'd
In Rooftop Rumble, KO Finish 3 players without leaving the bridge
Complete 30 Crew Contracts
Be the MVP of a three or four player team 5 times
Win matches with each Style of an Outfit
Catch a Sniper Shot
Throw a Caged player off the map
Complete the first 5 Training Levels
Win a match without being KO'd
Win a match without throwing a single dodgeball - Passing is allowed!
Play 100 matches
In Back Alley Brawl, Avoid a thrown dodgeball by entering a Tube
In Back Alley Brawl, throw a ticking Bomb Ball into a Tube
Win a match while having 5 or more Legendary accessories equipped
Win a match while having Legendary Glasses equipped
Win a match while having a Legendary Glider equipped
Score 100 KO Finishes with Ultimate Throws
Complete 100 Contracts
In Concussion Yard, KO Finish an opponent while riding the Wrecking Ball
In Galaxy Burger, KO Finish an opponent with a trash chute
Earn 100,000 XP
Complete 5 Season Contracts
Use 5 Energy Drinks
Complete 5 Event Contracts
In Galaxy Burger, fall through a trash chute
In Concussion Yard, ride the wrecking ball in for 15 seconds straight
Win 30 matches
In Knockout Roundabout, KO Finish an opponent while riding a car
Win 10 matches while grouped with a Friend
Win 5 matches while grouped with a Crewmate
Win a match while having an Uncommon (or rarer) accessory equipped in each slot
Win a match while having Legendary Gloves equipped
Play 30 matches while grouped with a Friend
In Knockout Roundabout, ride a car all the way around
In Rooftop Rumble, glide from the Bandstand to the Gardens
Earn 50,000 XP
Be airborne for 30 seconds straight while holding a Moon Ball
In the Hideout, tackle the T.A.R.G.E.T. Dummy off the roof