Funbro…

Well…
You obviously are pretty new to competitive play… OHKO a shuckle isn't that hard, as any body who use super effective move with plus 2 can kill that thing… Which is exactly what you did.
And the tanking shots part? What were they using a physical move on a Physical tank? A smart player switch in someone like Volcarona or ANYTHING with a fire type move and watch as you do nothing to them…
Plus Volcarona defends both your STABS, as well as quite a few other common types. Like Talon, Aegislash, Lucario, CHar, Excadrill.
All are tanky enough to take a 2x and In turn decimate you in their own special way.