Kinnara is beyond any doubt the best combination along Nico, you will incredible amounts of damage and with Nico as the primary hero you can inflict the DEF break with his active skill, then his with Kinnara a lot harder . Alternatively you can consider running Kinnara primary to be able to have the Control Tree active but you want Nico expertised as you can use Ambush in the Control Tree to practically have always the chance to inflight DEF break and then Nico will deal his 200 extra damage

Shadowblades works also great with Nico but that is because it’s an amazing marksman artifact all round