Is this a META build for [Kullervo]? No. Is this the fastest kill per minute build for [Kullervo]? Also no.

What is it, then? It's a very funny way to play [Kullervo], and if done correctly, you can absolutely merc level capped enemies with it.

Place Loki's Damage Decoy Augment in Empty slot (Not available on Overframe at this time)

Combine with a stealth/companion duplication build for [Shade Prime] and [Verglas Prime] and DO NOT USE WEAPON ATTACKS. As long as you stay within 24 meters of enemies and use only Warframe abilities, you will not break stealth. Cast Collective Curse on a group of enemies, then convert one of those enemies to a decoy and watch the fireworks...