As Number One and de facto team leader in The Umbrella Academy, Luther Hargreeves (Tom Hopper) has relatively plain powers compared to the rest of the team — but why does he have an ape body? Luther's abilities are one of the most classic superpowers: super-strength and enhanced durability. Relative to his six siblings’ abilities — which can prove difficult to control, to explain, or to define — Luther appears almost ordinary. That is, until one takes into account his humongous, apish upper body.
According to Sir Reginald Hargreeves’ numbering of the children, Luther is considered the most useful of the Academy. That may not mean he is the most powerful, but rather suggests that his powers are deemed useful in a greater range of situations than his siblings, whose powers may be more destructive (such as Ben’s or Vanya’s) or lend themselves to very specific tasks (such as Klaus’). His status as Number One also places him in a leadership position within the Umbrella Academy, a role he dedicated his entire life to, being the only sibling never to leave the Academy, choosing to stay by his father’s side.
Luther’s superhuman strength often comes into good use in a close-quarters fight or in dealing with criminal activity, as does his enhanced resilience. However, the limits of these abilities are not always clear. He can easily throw people across a room and is strong enough to momentarily lift a farm truck to free Diego’s leg, or punch a hole through a brick wall. The extent of his resilience is harder to define, since Diego was able to cut him with a knife and he is seen running from bullets, but in 1963 is seen using his body to stop a missile without suffering much injury.
His natural abilities were further amplified when, after a disastrous solo mission, Reginald had to save Luther’s life by injecting him with an experimental serum. The serum gave him an ape-like physiology, particularly in his upper body, which enhanced his pre-existing powers by greatly increasing his muscle mass and strength. Though a mysterious simian serum might seem like a peculiar way to try and save his life, the reason for Luther’s ape body is much wackier in the original Umbrella Academy comics than in the Netflix adaptation. In the source material, Hargreeves grafts Luther’s head onto the body of a Martian ape.
Though a long time has passed since his transformation, including four years spent alone on the moon, Luther continues to struggle with his self-image and his new physique. This manifests most obviously in his feelings of inadequacy towards his love interest and adoptive sister, Allison. His ape body in The Umbrella Academy season 2, however, appears smaller and less hairy than it did in season 1, but it remains unclear what the reasons behind this character design change are.