Nocturian

angron would, even tough kharn is really powerfull, he is still a astartes, angron on the other hand became a deamon prince, and he is a primarch (primarches are already way more powerfull then astartes by default).

Kharn could ofcourse still hurt angron, but kill him? no, angron would crush kharn in a battle, especially since this is the primarch of the world eater warbound we are talking about.

Kharn is however said to be khorns favored champion that puts him over even angron since khorn is the ultimate but I suppose that is simply because he collects more skulls for the blood god

well, yes, the blood god does tend to favore kharn more, but my point is that kharn wouldn't be able to angron as a space marine. You can compare it like this, putting up a assault marine againts a land raider. The assault marine has no means for actually pierincg the land raider's armour except for melta bombs (but he would actually need around 5 of time to get close to damaging the land raider criticly). Angron basicly is a daemon prince, he has increidble power, kharn on the other...