[@Parfex] What if, and I'm just spitballing here, Yours and Carlsberg's characters went to the same school but personally didn't know each other. She's a few years older but at a high school campus you would have still seen each other around, between the two of you y'all can decide on some kind of activity that the two of you would've taken part of during school that would've started the rivalry.

You then receive your powers from the fallen meteorite, learn about your powers and start to develop and nurture your powers while taking on the growing crime in the city and trying to start making a name for yourself as a hero, maybe something other than Vega as you decide after the time lapse to use Vega as your name. Maybe in the early days it's like Spider-man where your character doesn't have a 'superuit' and just runs around with a mask and a hoodie to hide your identity. Eventually you'll one day be using your powers when you open a black hole for the first time and are sucked into it, and then Interteller-esque your flung through time and arrive back in New Athens aged to 24 (maybe even 23 with a month or so before turning 24 to give your character time to adjust to the sudden change and time to acclimate), the black hole closing as soon as it sucks you in. Once out you learn your mother is dead, you read news articles on the black hole that you opened up and maybe learn that it caused some new science division (something that possibly was headed by STRIKE?) to be created in New Athens, that you were pronounced dead after going missing around the same time you created the black hole, and catch up on what's happened in the world that last however many years.

Then you get to the present day, I'd probably make it a few days after what's going on currently between Carlsberg and Jotunn's characters so your own character can learn about it through the newspaper or news channel. you see Dissonance from security camera footage or what have you and realize that she look familiar. Aha moment, it's her from school, she's evil using powers similar to your own, so in your righteous mind you're obligated to stop her (maybe thinking she gained her powers like you did).

If you do things this way we're not having to deal with multiple realities or universes but just a single universe where your character was flung several years into the future. No one has to change any of their plans, no storylines are affected, and no one is having to worry about two separate realities where Dissonance got her powers when you did and one where she didn't. Doing this your first fight with Dissonance will be just that, your first fight with Dissonance. This will strengthen the rivalry between you and cause you to try harder unlocking your other abilities.