? on counters

[bigdogdch]

Correct me if I am wrong in thinking this.
But would Primal Vigor and Corpsejack Menace create an infinite counter loop if you are able to place a counter on a creature?

[AeroSigma]

You are wrong, so I'll correct you 

Those are both replacement effects, that happen once each, you get to choose which applies first.

So you get a +1/+1 counter on a creature, and decide that Primal Vigor happens first.  Primal Vigor changes that to 2 counters.  Then Corpsejack Menace happens, and changes it to 4.  That's it.

See rule 613.5:

613.5. A replacement effect doesn’t invoke itself repeatedly and gets only one opportunity for each event.

Example: A player controls two permanents, each with an ability that reads “If a creature you control would deal damage to a creature or player, it deals double that damage to that creature or player instead.” A creature that normally deals 2 damage will deal 8 damage—not just 4, and not an infinite amount.