Not true--this isn't like sporogenesis where a creature token comes into play for each counter. The effect triggers on the creature going into the graveyard, checking to see if it has a counter, not how many counters it has.
That did just make me think of something though. Maybe I should change the wording so that it's "for each counter on that creature" so that if two of these are in play at once, the second one won't have its effect (partially) cut off by the first. I'll try that. Although now it's really texty. Hmm.
EDIT: now that I've done that, should I go back and remove the removal clause?
EDIT: Just thought of an idea I'd like to toss out:
Parasitic Wasps


{B}
Enchantment
Fading 3
When Parasitic Wasps comes into play, put a larva counter on each creature.
When Parasitic Wasps leaves play, destroy all creatures with larva counters on them. Put a 1/1 flying black insect creature token into play for each creature destroyed in this way.