Given the colors and creature type, this would be much more likely to have flying than first strike.

-3/-3 is a LOT to give out so easily. Check out Wasteland Strangler for a bit of a comparison. It gave -3/-3 once, and in a highly conditional fashion. This could perhaps get away with -1/-1. That's better than dealing 1 damage in most situations.

maybe this can deal -2/-2 once? Also, i will change it to flying

It's way too much for common. Kind of sucky as a rare, but tap to kill a creature is still pretty good at uncommon

I don't think it's fair to quite call this a 'tap to kill' for obvious reasons. However i will note this is quite good against decks running small creatures, it's comically oddly terrible against green, the enemy of both blue and black. Because green would often be running hyper-efficient creatures, and sometimes big ones at that. So this wouldn't take one out right away.

Also if a green deck is say running elves, a deck like that can survive without one, and if this happens to take out a combo piece, it's sad, because green usually has answers for that. Besides, they'll have enough ramp to get another one out next turn

Also green tokens would be immune to this, unless it takes out the tokenmaker (in which case it isn't that hard to get out another one), they still have 9000 other creatures ready to fight.

As for white, it can also do tokens, and it's iconics (as well as all iconics) are next to immune from this (maybe not hydras, but if you have a 3/3 green hydra you're doing something wrong :P)

So I agree this should be uncommon because it's very complex, but i disagree it's too good at uncommon. which isn't what you said, and I'm realizing that now. I think it's doable at uncommon. And I'd actually like to try somehting different with it...