Trent the pent up were wolf
Long story short, he's a werewolf (kind of). He's human most of the time but when he goes a long time without food, water, sex or anything he hypothetically might be addicted to, he becomes snippier and snippier and eventually starts to go through levels of transformation. He eventually become a beast driven by need for that thing. In that form he is humongous, large, and super hairy. And very strong (Aka grade-A furry tail).
Edit: More deats:
So here are some phase outlines:
Level 0: Totally human, incredibly reasonable and in control. 100% Human.
Level 0.5: Still totally human but snippier, a bit more aggressive, prone to emotions but mostly anger. Body is 100% human but starts to take some beastly mannerisms like constantly being tense, wary at the slightest sound, haunched posture, and some other various body language. (later stage 1 includes some more hair) Teeth are slightly sharper. Rational but frequently distracted by impulses and stimuli
Level 1: Mostly Human, becomes noticeably hairier all over. Pupils start to stretch vertically. Teeth are nearly werewolf like. Senses are wolf-like. Rationality like previous level but now loses himself in wolflike train of thoguht from time to time and may find themselves after a couple minutes in a place they remember coming but almost in like a dreamstate. Slightly stronger and more agile.
Level 2: Definitely not Human. Covered in light fur, body shape is starting to change noticeably. Hands and feet are now very paw like with a lot of fur and claws. Switches evenly between quadruped and bipedal walking. Recognition of human elements come and goes but is mostly gone. Rationality is frequently that of a wolf though it is a wolf that is smart and has self-preservation instincts though not human level thought. Extreme agility and increased strength (especially in regards to wolf like actions like biting). Constitution similar to that of a human. Just before this stage, the creature often leaves and does not come back and lives temporarily in the most wolflike habitat they can find.
Level 3: Full Werewolf
Level 3.5: Werewolf, Frenzy mode.
Got too lazy to finish, Basically it is a great design for a sex-adled beast of a man. (baddum-tsh)