Clear any scenario in Onslaught Mode. To make it easy on yourself, do the following:
- Character: Renault
- Class: Lumberjack
- Mode: Onslaught
- Difficulty: Easy
Leave rest of the options as it is and start.
Go towards the lamp posts and keep going forward. Don't bother picking up anything. You will pass by some tires on fire and then a van(?) slightly to your left. Go to the right of the van towards green healing item (pain killer). Stand there with your back to the corner. Equip the combat knife. Press LT to aim and just keep hitting RT to swing. If you have a turbo pad, it would be perfect.
You need to survive and kill 65 enemies in this scenario to survive the onslaught. You can see how many kills you currently have by pressing
Video guide here. Onslaught mode starts at 10:57: