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