No Pokemon is immortal •_•
If you train Shuckle in Def / SpD, it would make it hard to take down, but don't forget the HP stat. I suggest: 252 HP /128 Def / 128 SpD. If you go with Smogon.... then: 252 HP / 4 Def / 252 SpD
You have to rely on Toxic or some status to actually take down your opponent, since Shuckle has horrible Attack and Special Attack.