This is the hardest trophy in the game and will take some practice. So to clarify, stanley is just an AI opponent. Setup a 1v1 match against an AI with 1 bubble each on the blank map. You must fly toward the edge of the map and go out of bounds. The AI will follow you and if lucky they will drop a nuke and end up crashing into it, killing themselves in the process.
This might take a while to get right. It all comes down to luck.