What creatures are resistant to radiant damage 5e?

All except the shadow demon (which is still resistant) are immune to necrotic damage, and both shadow monsters are the only ones vulnerable to radiant. Yogoloths and oozes round out the resistances and immunities to acid. Undead, fiends, constructs, and true elementals make up the bulk of poison immunities.

Is radiant damage holy damage?

Radiant damage is essentially D&D 5e’s version of holy or divine magic. It serves as the sort of antithesis to necrotic damage and often stands in opposition to negatively-aligned creatures like undead and fiends. Basically, Radiant is the holy damage type of D&D 5e.