In comparison to Pantheon, Amumu, Shyvanna and Malphite, Sejauni, in my opinion, has greater carry potential.
Amumu is very stronger ganker and clearer, but next to other tanks he has difficulty reaching the back line, and he has no escapes.
Pantheon falls off extremely hard, as I'm sure you know and he is treated more as a fighter than an assassin, but he can't soak much either. His clear is pretty poor also, so he has a short window of time when he is very strong.
Malphite deals very minimal damage, but can soak as much Physical Damage as possible. He is very situational, but effective.. his carry potential is entirely in timing.
Shyvanna is super strong clearing and securing objs, but similar to Amumu has more difficulty isolating the backline.
So basically, of the other Junglers you listed, Sejauni is the most versatile with the most well rounded kit, with a lot of cc on top. With skill, she is the easiest to carry with, especially in solo queue since her Ganks are so effective and she has good clear too.
I mean, I wouldn't know to be honest, but hopefully that answers your question haha.
Good luck making it to Gold!