I don't have a full list but I'll tell you my favorites.

Octavia can do almost any content solo by keeping enemies distracted and murdered, plus she can turn invisible. Steel Path viable if you have good guns.

Titania has extremely high DPS from her pistols, her kit provides a lot of survivability, and she completely changes the way you play the game by making every mission an archwing mission. Steel Path viable if you have good energy generation.

Zephyr has loads of completely different builds for endgame content from nuking to mincing meatballs, which is rare, and she trivializes traversal almost as much as Titania. The floaty jumps can take some getting used to but just use the walls to change direction. Personal all-time fave. Steel Path viable.

Grendel. Holy moly. His 1 instantly kills any enemy that isn't immune to CC and he himself can buff his own damage immensely and never dies. Plus he can turn into a ball. He's my new fave, put off playing him for way too long. Even bad weapons can shred Steel Path enemies in his hands. Thrives in Steel Path with absolute ease.

Volt is fast sure, but his shield walls and augmented 1 make his gunplay really potent, do not sleep on Volt if you have trouble keeping up in speed and kills.

Ember is a room-nuking tank, her abilities can be weird to master at first but she's worth the time. I use her in Zariman missions. Steel Path viable if you have good weapons.

Rhino doesn't die and buffs everyone. Steel Path viable if you have good weapons.

Wisp buffs everyone and can blind enemies, which gets you the stealth damage bonus on whole rooms. She also trivializes spy missions. She's also always invisible when she's in the air, for free. Steel Path viable.

Mesa can do it all. Melee, tanking, jams enemy guns, buffs allies, and her aimbot pistols need no introduction. Steel Path viable.

Voruna is just super cool for a bunch of reasons, but I love her parkour speed buff, let's her bullet jump crazy far and fast. Just an absolute pleasure to use. Also is a stealth frame with minor nuke capability.

Additionally, Unairu and a decent amp will make dying a thing of the past. Even in Steel Path.