>>44357432Deino's life already sucks, being born blind, that should be enough but it gets worse.
Evolving it to Zweillous gives it a second, hostile, blind adversary that is biologically forced to fight and compete with it over food, and control of the body as only the strong head is allowed to retain its sentience upon evolving into Hydreigon, while the other becomes a mindless puppet hand.
A lifetime of blind pain and suffering invariably makes all Hydreigon into rampaging monsters that attack all things on sight.
Limit its suffering by letting it stay small and blind.