Does a creature with persist return if it had a +1/+1 counter on it when it died?

Persist reads: 'When this creature dies, if it had no -1/-1 counters on it, return it to the battlefield under its owner's control with a -1/-1 counter on it.' The key condition is that the creature must have had no -1/-1 counters when it died — but it says nothing about +1/+1 counters blocking the return by themselves.

However, the real interaction comes from the counter-cancellation rule (CR 121.3): if a permanent ever has both a +1/+1 counter and a -1/-1 counter on it at the same time, they immediately annihilate each other one-for-one. This means if a creature with persist already has a +1/+1 counter (from a previous persist return, for example) and then gains a -1/-1 counter, they cancel out — leaving the creature with no -1/-1 counter, which actually allows persist to function again.

So the answer depends on the scenario: a creature that dies while having a +1/+1 counter but no -1/-1 counter will still trigger persist and return normally (the +1/+1 counter doesn't block persist). The persist trigger only checks for the absence of -1/-1 counters, not the presence of +1/+1 counters.

Concrete example: You control a Strangleroot Geist (which has haste and persist). It dies for the first time with no counters, so persist triggers and it returns with a -1/-1 counter. You then use Cytoplast Manipulator to put a +1/+1 counter on it. The +1/+1 and -1/-1 counters cancel (CR 121.3), leaving Strangleroot Geist with no counters at all. If it dies again, persist checks — no -1/-1 counters — and it returns once more.

In summary: a +1/+1 counter alone does not stop persist from triggering. Only the presence of a -1/-1 counter on the creature at the moment of death prevents persist from working (CR 702.79a, 121.3).