If you haven't sacrificed any permanents during your turn by the time your end step begins, Sawblade Skinripper's last ability won't trigger at all. You won't be able to sacrifice anything during your end step in time to have the ability trigger.
Menace
, Sacrifice another creature or enchantment: Put a +1/+1 counter on this creature.
At the beginning of your end step, if you sacrificed one or more permanents this turn, this creature deals that much damage to any target.
, Sacrifice another creature or enchantment: Put a +1/+1 counter on this creature.
