Steelix

Steelix has fallen a long way from the titanic status it once had back in GSC, but that doesn't make it a bad Pokemon by any means. Its amazing physical defense and 11 resistances, including immunities to Poison and Electric, make Steelix a reliable user of Stealth Rock in UU. Its rival, Registeel, is more popular thanks to a wider support movepool and much higher Special Defense, but Steelix makes up for what it lacks with its unique typing, which is great offensively and good defensively, its access to Roar, and its Attack, which is just enough to pose a threat to its frailer would-be counters. It is also one of the handful of Pokemon who are immune to both Toxic and Thunder Wave. On the other hand, Steelix's shortcomings in its low Special Defense and Speed, defenselessness against Taunt, and common weaknesses in Water-, Fighting-, Fire-, and Ground-type attacks put Steelix at the bottom of the UU support ladder. Don't let these drawbacks fool you though, Steelix is a solid choice for any team looking for a Steel-type defensive pivot.