Perhaps an experiment went sideways, maybe it was just a fluke, but you now find yourself empowered by a fraction of the Space Stone, one of the six elusive Infinity Stones.
This grants you a generally enhanced body beyond the realms of what's possible for a human or kree to achieve naturally, and an internal store of cosmic energy you can call upon. Your internal store of energy is vast enough for you to empower yourself many magnitudes higher than your base, once you learn to control your output.
Enveloping yourself in your cosmic energy allows you to comfortably survive in the vacuum of space, tank large amounts of blunt force, survive targeted artillery fire from the Sanctuary II starship, and eventually even survive plunging through a planet's crust into its mantle and core.
Your cosmic energy benefits more than just your durability, granting the strength to send the likes of Thor across an ocean with a single punch, and eventually perform the aforementioned task of plunging through a planet's crust. You also attain the ability of flying at high speeds, being able to reach escape velocity within seconds and reach light speeds in space.
Your attunement to the Space Stone also grants you potent energy manipulation abilities in general. You are capable of firing destructive photon blasts, and absorbing energy attacks including things such as Thor's lightning. At your peak you will be able to impart enough energy to damage the likes of Ultron empowered by all six of the Infinity Stones.