Also, it's a conversation happening, right? When the player spends that first hold to reach the gang leader: "cool, how do you do that?" And after he describes it, you describe the reaction of all the people around him and the leader. That's your opportunity to make a setup move, introduce something that the PC has to react to (imminently) or not like the consequences. He might be face-to-face with the gang leader, but a half-dozen mooks are now staring down their barrels at him. "What do you do?"
Sure, he can then spend his second hold to kill or disable the gang leader. But once again, you say "sure, how do you do that?" and you've got the final say on whether he's killed or disabled and what that ends up looking like. You're well within your rights to have the gang inflict its considerable harm right then.
If he spends his third hold to avoid that harm, it's once again a "how do you do that?" with an bonus of "while you're disabling the gang leader?" Even if he comes up with something, it doesn't extricate him from the situation he's in: behind enemy lines with lots of attention on him and no more magic miracle hold. That's quite the spot. Also, the hardholder's gang is about to attack? What weapons are they using? Guns and grenades and molotov cocktails? Are they disciplined & skilled enough to avoid catching the touchstone in the crossfire?
I'm not saying Indomitable isn't wicked powerful, or that this wouldn't get old after a while. But the player shouldn't be able to roll 10+ and go "I spend 1 hold to get close to the leader, another hold to kill or disable him, and my last hold to avoid the gang's harm." "To do it, do it" applies to spending hold as much as any other move. Spending hold changes the fiction, and the fiction responds and evolves.