Maybe get the player controller and disable input once the player dies to prevent the user from adding velocity during this time?
Another solution would be to pause the movement in the movement component.
And a rather clanky solution for momentum would something like :
if(bPlayerIsDead && GetVelocity() > FVector(0,0,0)
{
AddVelocity(GetVelocity() * -1.0f);
}
meaning, simply pushing back the Actor’s velocity down by the negative amount of it’s current velocity.