Roselia

Even though she is not fully evolved, Roselia becomes a great asset to RU teams due to Eviolite. Eviolite makes her a great wall, boosting her mediocre Special Defense and pitiful Defense to formidable levels. Roselia also possesses a great support movepool that includes Spikes, Toxic Spikes, and Sleep Powder. Her pluses don't stop there; Roselia's ability, Natural Cure, is also a boon, as it allows her to shake off status effects and even cure herself from Rest upon switching out. Also, unlike other defensive Pokemon, Roselia boasts a decent base 100 Special Attack stat, which allows her to strike hard with a powerful STAB Giga Drain or Sludge Bomb. With an ideal support movepool, great defensive capabilities, and many other beneficial attributes, Roselia is certainly a Pokemon who will successfully fill the role of a defensive supporter.