Best solution for this achievement is to have a fully upgraded military truck
. You can unlock the military truck by completing the 2nd Blood Race Tournament.
Get close to your enemy and when approx. 1 car length behind him, hit the nitro/turbo (
). A fully upgraded military truck takes out smaller cars like the police car, muscle car or Ambulance etc. in 1 "nitro-ram". You probably have to ram a super car, bus or the other military truck twice, depends on damage taken by the enemy.
This is fastest done in the last tournament, as you have longer events (especially Elimination events). Otherwise try to work on it when going for the gold medals.
As this achievement accumulates the kills from races and from elimination events, it shouldn't take too much of your time.
Edit: If you have met the requirement previous to the update and the achievement didn't unlock and it's saying "Done! Unlocking...", just start another Blood Race Mode Tournament and kill an enemy with your ram. It should then unlock right away.