Here is the full list of all 18 Lethal Lawns: Competitive Mowing Bloodsport achievements.
Complete the Tutorial
Kill 100 opponents by mowing them down
Mow an acre (4047) of grass
Earn $100.00 from mowing grass
Steal $5 from opponents in Mowing Payday
Kill an opponent while their mower is disabled
Spin in a circle after winning a round, before the round resets
Kill the King of the Lawn 20 times
Win a round of Mowing Payday by $0.01
Win a game by winning every round
Kill 6 opponents from your mower exploding
Win at PayDay by mowing over half the lawn each round
Win a game of Last Mower Standing without dying once
Win a perfect round of King Of The Lawn
Watch a Custom Game between 8 bots
Ensure 25 deaths in the Backyard arena
Kill 50 opponents while they are mowing grass
Mow the entire lawn in a round