Sucker shotted by Atlas, when his cosmic awareness was off, so he wasnt able to amp his physical stats/durability or put a shield up. Keep in mind, Surfer's been knocked out by Karnak throwing a brick, as well as held in place unable to move by Black Panther. He was shown more powerful than Zemo, someone who owned the Grandmaster and was called the most powerful hero on Earth (after Photon was dead). Zemo only won with alot of help from Blackout. It was made quite clear Zemo NEEDED Blackout because Zemo couldnt beat Photon on his own. And Photon beat Sentry.
You're talking about the Sentry/Genis fight? That was a HUGE fight dude. First off, Genis was at a disadvantage. Not only was he distracted trying to tune his cosmic awareness, but also distracted trying to watch out for the well-being of Cap. Secondly, they destroyed multiple planets in that fight, one on-panel, multiples by the narration, and one found out later on by Hyperion that they also destroyed his planet. And the fight went for almost the entire issue, most of it was just off-panel. And Genis was shown at the very least to be slightly superior.