2 counters will be done.
I will put deadly venom on upped.
cost 4
for both?
The ONLY way for you to put poison counters on your own creatures is by using

Parasites ,

Death Nymph or

Toadfish. Ignore the toadfish as it makes the deck a trio.
There aren't that many scenarios where you would face an opponent using infection as creature control.

Spine Carapace,

Plague, Death Nymph, Aflatoxin, and Virus are the only ones I see here.
Even with a Parasite already out on the field, you need 6

, 2 from using infection and 4 from this card, to give a creature the Venom ability. Costs even more with Death Nymph. As others said above, it's totally underpowered. Reduce the cost to maybe 2/1 and make both versions give deadly venom.