Can your opponent use monster reborn on your destiny end dragoon?

Yes, your opponent can use "Monster Reborn" on your Destiny End Dragoon, as long as it is in the Graveyard. Destiny End Dragoon does not have any protection against being targeted by effects like "Monster Reborn." However, if it was destroyed by a card effect that specifically mentions it cannot be targeted or revived, then it would not be possible for your opponent to bring it back.