Infected - 1 Avatar

Bloodrayne:
Complete all missions.

Chimaira:
In mission 29, kill a zombie near the Chimaira sign, then get the avatar that it drops. The sign is located in the long street section under the park at the top of the map.

Easy combos:
When you get the chainsaw, combos become easier. Stand over a Manhole and use your chainsaw to get high combos. Manholes with lots of enemies around them are recommended, as you can get up to a ten combo with one slice.

Santa Claus:
Complete all missions.

Slipknot 0
In mission 5, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located almost in the center of Time Square.

Slipknot 1
In mission 7, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located in the subway.

Slipknot 2
In mission 10, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located by the helicopter.

Slipknot 3
In mission 13, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located in the upper left section of the map.

Slipknot 4
In mission 16, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located near the landing zone.

Slipknot 5
In mission 20, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located in Time Square.

Slipknot 6
In mission 23, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located in the bottom section of the map.

Slipknot 7
In mission 26, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign can be found when the mission is started.

Slipknot 8
In mission 31, kill a zombie near the Slipknot sign, then get the avatar that it drops. The sign is located in the bottom right section of the map.