Such a sad end...

[martinuzz]

Such a sad end indeed. Eol died without even summoning on me once

Still, I wonder if there really is no other, more peaceful way to complete that quest than killing him.

[IckyThingBane]

There isn't, but don't waste your sympathy. If you've ever read the Silmarillion, you'll know he's a fairly unsavory character - forcing his wife into marriage, keeping her and his son Maeglin prisoner, trying to kill his son, etc...