Here is the full list of all 18 Lethal Lawns: Competitive Mowing Bloodsport achievements.
Earn $100.00 from mowing grass
Kill the King of the Lawn 20 times
Kill 6 opponents from your mower exploding
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 100 opponents by mowing them down
Kill 50 opponents while they are mowing grass
Ensure 25 deaths in the Backyard arena
Mow the entire lawn in a round
Mow an acre (4047) of grass
Win at PayDay by mowing over half the lawn each round
Win a game by winning every round
Complete the Tutorial
Win a round of Mowing Payday by $0.01
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