That’s a betta fish.
Safe with most community fish, but known to get very aggressive. Nowhere near as bad as most cichlids, but can be a danger for look-alike or slow moving fish.
I wouldn’t recommend mixing with puffers, as the long flowing fins of the betta are a target for the fin nipping puffers (and the fighting that ensues wouldn’t be pretty). Best to setup a small, well planted, 5 gallon tank for it.