Victreebel

Victreebel is widely regarded as the most immediately dangerous weather sweeper in the metagame. Due to its solid offensive stats, Chlorophyll, moves such as Sleep Powder and Weather Ball, and its Toxic immunity, it can harass offensive and bulky teams alike under sun. Its strong Grass-type STAB moves in Solar Beam and Leaf Storm are especially effective at threatening metagame staples such as Regirock and Slowking.

Nonetheless, Victreebel's Speed outside of sun and bulk are pretty lackluster, and weaknesses to common types such as Fire and Psychic make Victreebel easy to revenge kill and hard to bring safely onto the field. Therefore, it relies a lot on sun to accomplish anything against offensive teams. Furthermore, while Victreebel is certainly powerful, its Special Attack isn't enough to reliably break through common special walls such as Cradily, Lickilicky, and Hypno. The omnipresent Skuntank is also very troublesome, as it resists Victreebel's STAB moves and threatens it with Pursuit and Sucker Punch.