Jekyll

Jekyll is a white scarred Junkyard cat that spends most of its time fleeing, only attacking with a multi-hit melee if it has nowhere left to run. Its true threat is temporal: after 3 turns it transforms into a Hyde, retaining any damage already dealt to it. Killing it before the transformation is critical — the wiki's advice is blunt: "Kill them with extreme prejudice." Cornering it early forces it to fight rather than flee, making the most of its limited health before Hyde emerges.