Tribes: Ascend/Perks/Super Heavy
"Increases mass by 40%, making it harder to be knocked back when flag blocking. Final unlock damages enemies that run into you."
Super Heavy increases the mass of players, preventing them from being knocked around so much by explosions. The final upgrade prevents the player from taking damage when a vehicle tries to run them over, and also causes damage to players who run into them. This is a Secondary Perk.
Upgrade 1: +20% reduction
Upgrade 2: +20% reduction
Upgrade 3: Body block causes damage.
Flag defenders use this perk the most. Heavy armors generally stand on the flag with this perk to prevent people from grabbing the flag. Infiltrators also like to use this perk, go invisible, and then intercept a player going for a high speed grab, instantly killing them by blocking their way.