I'd recommend doing the "fake" multiplayer glitch for this trophy, which you can find how to do here: https://pastebin.com/Jgf6vPeJ
Before starting the round, make sure you vote for the Snowball version of Tumble in the vote menu. Alternatively, when you're creating the round, go into the Settings and set the game type to Snowball only.
Once the round starts, if you're using my method above, switch over to the "fake" player two account. Once there, simply get them to jump off the map into lava, and the trophy will pop.