It’s difficult to pin any specific tactical shotgun down as the most powerful. What I can do is say that as a category, 10-gauge tactical shotguns will be the most powerful tactical shotguns available. But more power isn’t always good. As we briefly discussed above, more power also means more recoil. 12-gauge already packs a punch, even with the lighter recoil of a semi-auto. 10-gauge is even worse.  Plus, 10-gauge rounds are bulky so it’s not easy to carry spares on your person. And to top it off, 10-gauge isn’t even better for taking down the targets you’re most likely to be encountering than 12-gauge is. Unless you plan on stopping vehicles, 12-gauge is plenty powerful enough.  12-gauge ammo is also cheaper by far and much easier to find in stores.  Bottom line: 10-gauge tactical shotguns are more of a novelty for the range than a practical tactical weapon.