Vengeful Warchief

• WWizards of the Coast2019-07-12
  Official Ruling
  If Vengeful Warchief comes under your control after you’ve already lost life in a turn, its ability can’t trigger during that turn.
• WWizards of the Coast2019-07-12
  Official Ruling
  A player loses life if they pay life.
• WWizards of the Coast2019-07-12
  Official Ruling
  If you pay life to cast a spell or activate an ability, you don’t put a +1/+1 counter on Vengeful Warchief until after you’ve finished casting that spell or activating that ability. You put the counter on Vengeful Warchief before that spell or ability resolves.
• WWizards of the Coast2019-07-12
  Official Ruling
  You put only one +1/+1 counter on Vengeful Warchief, no matter how much life you lost.

Rulings via Scryfall