To be blunt about it, I was playing custom robo, and a friend told me to try using one of the lowest defense robos in the game (it's maneuverable if you need to know why I used it). At the same time I was using a bomb that does no real damage and launches you instead. I forget what the rest of my loadout for this battle was.
So yeah, squishy robo + Bomb that does no damage x Arena with lava in the corners = somehow winning so easily that it almost felt like a joke.