Ride 'Em CowboyG 25

To unlock this achievement you simply need to Rodeo kill a Titan while there is an enemy pilot inside it. You must jump onto the back of the Titan, rip off the protective plate exposing its wires and circuitry. The last step needed to take down a Titan would be to aim you primary weapon or sidearm into the newly exposed compartment and shot it until the Titan enters a Doomed state. You can not use a Anti-Titan weapon as it will kill you first. If you use the Spitfire LMG as your primary weapon there is a special mod that you can equip that will deal out a massive amount of damage to Titans for this achievement.