Is Hellhole Flailer legal in Standard, Modern, and Commander?

Hellhole Flailer is legal in: Modern, Pioneer, Legacy, Vintage, Commander.

Hellhole Flailer

Q: What type of card is Hellhole Flailer?

Hellhole Flailer is a Creature — Ogre Warrior. Its oracle text reads: "Unleash (You may have this creature enter with a +1/+1 counter on it. It can't block as long as it has a +1/+1 counter on it.) {2}{B}{R}, Sacrifice this creature: It deals damage equal to its power to target player or planeswalker."