My favorites all time unit?The Death of a Thousand Bites
Necron Destroyer Lord, with the scarab swarm Cape. They're all jet bikes, and have a 2+ cover save super easy. War Scyth, gaze of flame, lightning field, and nightmare shroud. Scarabs with disruption fields.
Prowling around the edges, scaring the little ones(IG, Lootas, TAU).
They eat both infantry and vehicles alive. Mobility, destruction