Thoughts on each DLC:
Min Min: A nice character to have from ARMS, but it sucks the reveal was underwhelming. She was broken with her long range attacks.
Steve: One of the best inclusions, but also really fun to play. He captures the element of Minecraft very well with blocks and crafting.
Sephiroth: A surprising pick, but nice to see him. His long sword is always deadly with the annoying shadow flare.
Pyra/Mythra: Best DLC character and one of my mains. Wanted them since Ultimate was revealed and they're so fun. Xenoblade is awesome.
Kazuya: Didn't like him at first, but overtime I got the hang of him. Now he's a secondary for me. Well represented as a Tekken character.
Edit: No longer a secondary. He's my main alongside Shulk, Aegis, and Hero. EWGF carries!
Sora: An amazing addition in the game, with no convoluted Kingdom Hearts lore. Jokes aside, he's super floaty but fun to play as.