List of OP upgrades:
1. Invincible when boosting - Can I even start?
2. 50% chance of quad shot when boosting - Yeah.
3. 50% chance of lightning storm when hurt - Very useful for clearing out crowds of enemies to prevent further damage.
4. 30% chance of orb when boosting - Very OP when combined with upgrade 2 on this list.
5. Better handling - More precise driving.