How is that OP?

Probably because he can also sense every information with his vision, such being able to see everything even through walls and with dismantling or changing the information can also kill nearly every person without effort, change or suppress every magic in his area, destroy or change every matter, is additionally on master-level in martial arts, a genius who overthrows the magical standard multiple times, can use the most effectic and rare anti-magic technics because of his unusual great psion count and can cast magic without the help of a CAD, such being one of the fastest in actual combat.

Yeah, Tatsuya isn't and all-round talent, but especially in terms of combat power he is easily on another level, with literally only a few people on the whole world being able to fight him in an even fight. I mean all of his struggle literally comes from the point, that he is too powerful and isn't allowed to show his real strength... and that isn't even the whole level of his abilities, as he later shows in the LNs...

I do like Tatsuya, mostly because his powers works in the worldbuilding and the rules of the magic system and he's more of the "Genius who used his few assets right"-type, but of course he is outright OP. His powers are way above both the standard in this world and his enemies in battle, he doesn't even need to struggle to win in actual combat.

The biggest problem with the "overpowered" is how the meaning changed from "way more powerful than the standard/opponent" to "the character didn't earned it". Mostly because we had so many asspull characters/endings that made no sense. Being overpowered doesn't mean the character doesn't earn it somehow, it just means, that they are way stronger than the norm/opponent. And in this quite limited time frame that's also true for Ikki. With all his power unleashed, he is way stronger than his opponents. They managed to give him a better limiter, they made him earn his power with work/wits and his power has a way clearer defined ruleset than Ayato's, but inside this one minute, he's still overpowered in the non-judging meaning... which is a common trope (the loser/outsider who has a hidden power) and that's why those characters are thrown together. More so because we start with Ikki at the point, where he already owns his power, introduced as the loser who can beat the prodigy...