What happens in Las Venturas...

Complete "Yay Ka-Boom-Boom".

Story-related trophy/achievement. You will unlock this after completing Yay Ka-Boom-Boom, which is the final story mission in San Fierro. This mission isn’t too bad, although you will have to kill a bunch of enemies. As long as you take your time and kill the enemies before driving forward with the bombed car, then you will have no trouble.