Polyraptor

If multiple sources deal damage to a creature with an enrage ability at the same time, most likely because multiple creatures blocked that creature, the enrage ability triggers only once.

If Polyraptor leaves the battlefield before its triggered ability resolves, most likely because it was dealt lethal damage, the token will still enter the battlefield as a copy of Polyraptor, using Polyraptor's copiable values from when it was last on the battlefield.

If lethal damage is dealt to a creature with an enrage ability, that ability triggers. The creature with that enrage ability leaves the battlefield before that ability resolves, so it won't be affected by the resolving ability.