Mayhem 3D
38 Achievements
8-10h
Pile Up
Hit 4 opponents with a single ramming speed boost (excluding challenge events)
18.1%
How to unlock the Pile Up achievement in Mayhem 3D - Definitive Guide
Demolition Derby
The Taco
Use a later leveled moster truck
11 opponents/Normal/Monster Truck opponents
When you start, just back up and get as much boost as you need for your ramming speed. Drive out to a corner and charge. All of the opponents should be congregated in one part of the level. It may take a few tries, but if you line them up properly, you'll be good to go.
Exhibition
Banger Race
Sidewinder
Get any car with good traction ( I chose muscle car #30)
Turn boost to infinite
Start race
Build up you ramming speed the normal way but it helps to stay in the back of the pack so you get a larger boost at laps end. Once your ramming speed is built up wait till ur at the long straight away with several cars in front of you (again it pays to hang in the back of the pack) then drive and just hold boost. even tho your boost meter will decline you'll never lose the white ramming speed hue meaning every car you hit becomes debris. As long as you don't drive of course or hit a wall n stop you can use this... Infinitely. I got this in lap 2 and destroyed 30 cars between lap 2 n 9 since I didn't hit walls.
You can say that this is the hardest trophy in the game, but it's not that hard. Select a race which has a straight road in Exhibition with 11 opponents in sedans or trucks and 9 laps. When the race starts, start ramming some racers until you get enough boost in the gear to use ramming speed, then wait for a line of 5 racers. When you see it, start ramming them until you hit 4 in a row in one ramming boost.
To use ramming speed, wait for the gear on the bottom left corner to be fully red, then both the skeleton and the gear will turn red. Aim at cars and then press and hold to destroy them.
NOTE: Cannot be done in Challenge events (Challenge events are in Career, each chapter will have a Challenge as the last event).