In Lava Reef Zone Act 1, you will eventually come across a metal walker contraption sat on a platform near some lava.
You need to cross the lava with it, which is patrolled by Rexon (Purple dinosaur looking thing) and crash into it.
To make the walker move jump on one of the legs of the walker so it moves. Keep on jumping from leg to leg.
To unlock the achievement you need to be moving across the lava using one and crash into a Rexon.
Midway through the Act 1, there is a perfect point where there is a couple in a row next to a walker's legs with a shield box under the legs which you have to go past.
For video guide please watch the video below. Thank you Eurydace for creating it: