From The TimeSplitters Wiki

The Freak
Unlocked by	Default
Species	Mutant
Size	Normal
Accuracy	N/A
Agility	5
Stamina	5
Fire Proof	5
Shock Proof	5
Default AI	4
Native TimeZone	2052
First Appearance	TSFP Story Mode
Relations	Hybrid Mutant, Berserker Splitter
Games	TSFP

TS1 Gesture	N/A	TSFP Gesture	Raises arms in air and makes a noise
TS2 Gallery	N/A	TSFP Gallery	An everyday story of genetic manipulation gone wrong-at least on the bright side he’s resistant to most common crop diseases.

The Freaks were Crow's first attempt at making a TimeSplitter. The have a striking resemblance to the Hybrid Mutant due to the fact that both are half human and half Splitter.
In the single player game the only effective way of killing them is by use of the dart gun which causes them to explode dealing damage to everyone in a close radius. Also, they can create bursts of energy from their body.You can kill them with bullets too, but you have shoot them in the head a few times.