I used a jump spell with 50 magnitude and jumped in a tree and used spells on him

you can probably use a bow but i didn't have any arrows.

If you use spells you will probably need the unlimited health cheat code because he will
deflect a lot of the spells.

it took me some time too it's nearly inmpossible to hit him but get a weapon skill to 100
and ur agility to 100 and maybe some enchantments on ur equipment to increase them
(constant effect is best u can use the soul of a golden saint or vivec to do this) and if
u are patient enough you'll hit him regularly and he'll die (eventually)

use a steel war axe on the little prick or a mace or even better a degaric cloymor