Haxorus is also underrated. All it needs to do is be the recipient of a Shell Smash or even just a Rock Polish (Mew is great for the latter and also for setting up Dual Screens) and you've got a fine sweeper on your hands. Especially if you had Mew set up Dual Screens and your Haxorus is the "Bulky SD" variety. You could even have a Smeargle pass Ingrain to a Mew with Dual Screens and Rock Polish passing to a Bulky SD Haxorus, just for the epic sweep, and have three other party members who rock in their own way.
Garchomp can also be the recipient of Shell Smash. Or better yet, Hydreigon (who can use all three offensive boosts). I can't tell if you're serious here. A lot of Pokemon are great when passed a Shell Smash (Bibarel..), it doesn't mean they are underrated. It just means they require more support than other Pokemon, and are STILL outclassed.