Interesting. I think it’d be a signpost uncommon.

Okay firstly, templating.

Secondly, a 2/2 for FIVE mana that hates on counters and can't be blocked if they control a single non-basic is still pretty bad. I want to be winning the game on turn 5, not playing a creature that can swing in for 2 or maybe 3 damage next turn.

Thirdly; Colour. Why is this rakdos? White is the colour of fairness. What is red and passionate about this card?

Well, it's not really fair. It's "Gimme all your counters". So sure, red for the emotion of greed. I do agree this is probably too late for the effect. Though it's a very strong effect. Like "This card exists? That deck archetype cannot exist". Which makes this a sideboard uncommon rather than a build-hint uncommon.

To be a build hint... cheaper and gains a copy of the tokens? To be a usable anti-deck-sweeper at this cost - how about it hoovers up all counters that exist when it ETBs?

Assuming that the '+1/+1 etb' is instead 'a +1/+1 would be put on a creature'... that still goes a bit funny if you have two of this in play. That plus doubling season is infinite I think; but that's in the general pool of "Doubling season goes infinite" and not really worth worrying about.

Being unblockable over a nonbasic land feels red. The counter taking probably bends out of black removing counters, though I don't know if there's a color that already takes counters from opponent's creatures in such a way.

At five mana, it is quite expensive for a small body.

While I at first took this as meant to hose opponent's an opponent's playstyle, the right environment this could effectively be a big beat-stick as this accumulates your other +1/+1 counters (and it's not like black doesn't have indestructible instant spells)