Except his initial cost is 1
Sure, his play cost is 1... But he's also completely worthless if you
only spend 1 resource on him. And if you invest too much on him, your opponent plays removal and you're fucked.
Anything else that is even remotely close to being this powerful costs 7+ mana, which means if you play it and it gets killed off, you've paid a large opportunity cost.
And what do you get with Alpha One for 7 resource?
A fucking blank 12/13. Of course, you can use his 6-resource ability and then he'd actually be good, but the point is you've just spent
thirteen resource on a single creature. Which means if your opponent manages to land a removal on him you might as well concede now. Also even if he lives, you'll have to spend
another six resource on him next turn if you want to keep him useful.
Not to mention it's hard to even keep him alive for long enough to buff him to 12/13. There're various removals and pseudo-removals that can hit creatures in support (Annihilate, Kidnapper, Fight!, Called Shot, Assassinate...), and even more removals that threatens to kill him as soon as he enters a combat zone. Putting him in command would be even worse, because he dosen't contribute to your deck's purity and can be killed by an early Lightning Blast/Firebolt. And don't tell me that this is rare -- god knows how many Secluded Constructors has died to a turn 1 Lightning Blast.
What creature would you honestly rather have them him?
Uhhh... Too many to count?
If you want an example, how about
Immovable? He only costs 5, has Vigilance so your opponent can't target a removal on him before he enters the combat zone, and he pretty much stops any aggression for at least one turn while potentially killing off 3 or 4 enemy creatures. If I wanted to complain about balance,
this is the card that I would complain about.
The argument that he's not OP because he can die is stupid. Fucking everything can die.
Yes. And that's precisely why it's a bad idea to invest 10+ resource on a single character that isn't removalproof.