who is the evil elf in rings of power

The character you are referring to is Adar, the evil elf in The Lord of the Rings: The Rings of Power. Adar is a dark elf who is the leader of the Teleri, a faction of elves who worship the Dark Lord Morgoth. Adar has sworn loyalty to Morgoth and seeks to destroy the other factions of elves who oppose him. He is a powerful and ruthless enemy who will stop at nothing to achieve his goals.