Pay {0} to activate Outrider en-Kor, targeting Task Force.
Task Force triggers, giving itself +0/+3 untill end of turn.
Repeat steps 1-2 untill Task Force has infinite toughness.
Sacrifice Task Force to Life Chisel, gaining life equal to its toughness.

Infinite lifegain

Outrider en-Kor

Task Force

Life Chisel

Activate Life Chisel by sacrificing Su-Chi.
Su-Chi and Nim Deathmantle triggers.
Resolve the Su-Chi trigger, adding {C}{C}{C}{C}.
Resolve the Nim Deathmantle trigger, causing you to pay {4} to return Su-Chi from your graveyard to the battlefield, and then attach Nim Deathmantle to it.
Resolve the Life Chisel trigger, gaining 4 life.
Repeat.

Infinite death triggers

Infinite creature ETB

Infinite lifegain triggers

Infinite creature LTB

Infinite creature sacrifice triggers

Nim Deathmantle

Su-Chi

Activate Life Chisel by sacrificing Su-Chi.
Su-Chi triggers, adding {C}{C}{C}{C}.
Resolve the Life Chisel trigger, gaining 4 life.
Activate Kenrith's fifth ability by paying {4}{B}, returning Su-Chi from your graveyard to the battlefield.
Su-Chi enters the battlefield, triggering Carnival of Souls, adding {B} and causing you to lose 1 life.
Repeat.

Kenrith, the Returned King

Carnival of Souls

Combos with "Life Chisel"