Sorry the little one is taking a beating. Adding them a month or two apart is a classic setup for this; the first fish often decides the whole tank is theirs, and the second never quite gets equal footing.
A few of the tips already posted are solid (acclimation box, extra hides, the bucket reset). Since the bucket trick calmed things overnight, keep watching for a few days. If the chasing comes back hard, I'd park the bigger one in an acclimation box for a week so the little one can claim some space, then try them together again with lights low.
For recovery on the beaten fish:
- Make sure it's still eating. Soft frozen or a small pellet it already knows helps it bounce back.
- Watch for cloudy eyes, fuzzy patches, or clamped fins that get worse; scrapes can pick up a secondary infection.
- Give it real cover: rock caves, not just open sand. If it has nowhere to duck, the bullying doesn't stop.
If after a solid try (box, hides, and time) the big one still tears it up every day, they may not be a pair. At that point a permanent split is kinder than forcing it. Some clowns just don't settle once that hierarchy goes sideways.
Mike / Blue-Eyed Clowns