The first two modes pretty much equal a Skullcrack since the Command cycle allows you to choose two of the four modes. Losing the damage prevention restriction from Skullcrack and adding the ability to hit each opponent isn't a big deal. The each opponent addition does seem odd, as this isn't a card you'd expect to be good in a multi-player format. But, it’s there all the same.
How about the other two modes? The ability to play a land card straight to the field is an interesting option, and it probably will be the most rarely used. Still, don't rule out using it, especially as that land can come in untapped. The last mode may easily be the best: giving creatures you control +1/+1 plus reach until end of turn. Reach is actually pretty good since Red/Green does have problems with flyers. Of course, that means using this card defensively in decks that want to focus on being constantly on the offensive.
The obvious home for Atarka's Command was Gruul Aggro, an aggressive deck featuring the Green mana mostly just to play the Command. Another deck that spawned using the card was Atarka Red, which played another powerful Green card called Become Immense. Not only was Atarka's Command good in Standard, it was good enough for existing Red decks to add Green mana just to play it. The two decks eventually merged into Gruul Deck Wins, a strong deck in Standard that eventually just became known as Atarka Red.
There were already enough incidental life gain effects in Magic at the time that a card like Atarka's Command became a solid tempo card. Creatures with lifelink and cards with life gain effects like Siege Ehino being neutralized was a nice boon for aggro decks. The sheer versatility of the card, as well as the extra land drop at instant speed, made it an instant hit in the red/green decks that wanted to play hard and fast.
In Modern, Atarka's Command found homes in the popular Naya Blitz deck as well as Bushwhacker Zoo. It was particularly good in these Red/Green/X decks due to the presence of Burning-Tree Emissary, which adds a Red mana and a Green mana to your mana pool when it enters the batlefield. It would also find its way into Red Deck Wins variants and Burn decks that splashed Green just for the Command and the sideboard card Destructive Revelry.
Well into 2019, Atarka's Command still sees play at four maindeck copies in Modern in upgraded versions of decks like Atarka Zoo and Bushwhacker Zoo. Most recently, Atarka's Command has made its way into the sideboard of Modern Goblins. These Goblin decks now run Green mana because of a new Legendary Goblin Grumgully, the Generous, who is Red and Green.
Atarka's Command in Pioneer
With the annoucement of the Pioneer format - which begins with the Return to Ravnica set - many cards like Atarka's Command that were powerful Standard cards in the past are getting another look. As this is a card curently seeing Modern play, it's no doubt that we'll see this versatile instant see play in a format alongside cards that it has seen success beside, such as Burning-Tree Emissary and Reckless Bushwhacker.
Without a doubt, Atarka's Command is one of the more versatile two-mana instants out there. It's both good for tempo and burn. This is a card every Magic the Gathering player should try to have in their collections.