Is he any good in pvp?
Yes and no.
Yes
It has metal slash so if you don’t yet have Vegitiger, he’s not bad.
No
Shadow - OHKOed by holy type
Angel bane - was supposed to be great against angel but as angel is a type whom it’s weak against, it hardly does 1/3 of luxknight hp.
Its aoe is not bad due to its high physical attack
All & all, there are better ones. Its quick so would most likely get one of first turns. But I don’t use shadow arks in pvp due to its weakness against holy arks which are very common in pvp. So depends what your other arks are & your whole strategy.
Thanks.