Berserker is a unique hero who nearly breaks game mechanics in order to deal dangerous amounts of damage
Bronze, Rage Fire: Berserker goes into a rage and his field of View is reduced to merely the radius of the aim (the horizontal and vertical lines if you know what I mean) but he vastly improves basic weapon damage and rate of fire. If AI controls him he is disoriented instead.
Silver, Throw of Death, Berseker destroys his cover to throw it at the enemy, dealing a great amount of elemental damage. If his cover is destroyed already he throws himself instead and deals damage to himself.
Gold, anger management: Berserker has improved accuracy overall and deals bonus critical damage
Platinum, revenge plan: each time an ally dies Berserker stuns the killer with a strong bash with decent damage