>>37848416GSC and RSE E4 are challing for the fact some rely on insane and easy to perform RNG tactics and even if those don't win the battles most of the time they end cutting half or more player team's PPs and healing items between status and self damage healing.
Phoebe is one of the most hardcore ones at this with Pressure, Curse, like every possible status, bulky fucking Dusclops that also hits relatively hard, Agatha in FRLG, Glacia and Attract + Paralysis isn't any funnier either if you don't have the right starter or type advantage.
To some these trainer teams may look stupid but they will realize their purpose only once they reach the last E4 member and champion, higher level and slightly stronger Pokemon movepools are quite a threat after you lose most of your healing items.