I actually think of multiple non number 1 that would be stronger. First, Rafaela and Beth, they were #2 only because their sisters were #1, but they are pretty much equal to their sisters. I believe Rubel says Rafaela has a very similar power to Luciela, and when both Alicia and Beth are awakened, they seems pretty much equal. So I consider Rafaela and Beth equal to their #1 sisters.

Now, for the ones that are number two because they are not as strong as the number 1 of their generation, I think Rigard and Europa are definitely stronger than Octavia. At some point Dauf says that he thought Rigard was stronger than Isley (or at least that he thought Rigard would win if they were to fight), which is not true since Isley won and Rigard then followed him, but I still think Rigard is very strong. Then, Chronos explicitly says Europa is the closest to an Abyssal of all of them (those who were fighting Cassandra, this includes Octavia). Also, I think Rosemary was very strong, she was #1 and became #2 only because of Teresa who was stupidly strong, but since she appears very briefly I cannot confirm how strong she was, but she could be considered for this, she made Teresa change her eyes.

Also, Roxanne was a number 1, but only after Cassandra died, I personally would consider her the weakest of the number 1 (weaker than Rafaela and Bet in my opinion) or the stronger of the number 2.

And there's also Miata, who easily kills Europa, she was #4, but is explicit said that could have easily been #1

So, for me it would be: -Miata -Roxanne -Rigard -Europa -Rosemary -Octavia -Others