Brand is one of the most powerful AP Supports out there and just so happens to be a fantastic scaling Champion. His kit revolves around doing percentage-based damage, which gives him great stats, to begin with. This only grows as the game progresses, with Brand becoming more robust and able to obliterate health bars like there’s no tomorrow.
Bard is often named the biggest troll Champion ever to release in League. However, I’d attribute that title to Ivern, who is miles worse. Bard’s kit is designed to scale with the game, and each passing minute makes Bard better overall. He starts weak and slow but gains a lot in might and utility as the game progresses.
Zyra is, alongside Brand, one of the most powerful AP Supports out there. She focuses more on doing damage and harassing than anything else. Differing wildly from the popular Enchanter Supports, Zyra has a thirst for blood that has to be satiated. Zyra can pin the enemies into place and do tons of damage to them by using her plants and roots.
Senna is best described when compared with Kindred. The Champions can have infinite scaling, and it’s built directly into their passives. While Kindred requires killing particular Jungle camps and Champions, all Senna has to do is damage. Whenever she attacks an enemy Champion, she’ll get a passive stack. She also gets them from fallen minions in her proximity.
Thresh is infamous in Bot Lane for his ability to pressure the enemies. A hook to the face will immediately punish every opening, often followed by a swift death. Thresh can, through mere presence, establish a level of dominance in the Lane. It causes his enemies to play in a particular way, stand in just the right spots, etc., throwing them off course.