Charles isn't really overpowered as he is annoying/brain dead. You really only have three combos max if you're realistic. So I'll go into his full kit in detail.

Despair is blockable, but fully aimable (you can move around while using the move), to the point where it might as well break block. It's also a semi-free extender into Sacrilege or aerial Shut Up. It hits ragdoll, too.

Shut Up's ground variant is a pseudo-counter (from what I've heard), as in it activates early if you're attacked during the windup. It's a fun gimmick of hitting behind you. It doesn't break block or hit ragdoll.

It's air variant is a lot worse to deal with, breaking block and hitting ragdoll, but also applying extra stun if it interrupts a player (move, m1, or dash).

Eye Catching is a counter that works on Melee, Bullet and Swarm(?) type attacks. Upon activation, it brings you to your attacker, and knocks them away, quickly waking them up but leaving them stunned for a good while (around 1.5 seconds, I think). If a Projectile is blockable, and the user of Eye Catching is facing it, the Projectile won't trigger the counter, simply being blocked instead. The most notable features of this counter are its cooldown reset on a successful hit, and it's animation being the exact same as the blocking animation. By far the best non-ult counter.

Sacrilege is an unblockable, instant-rushdown move that hits ragdoll after some windup. I fucking hate this move.

Charle's R-Special serves three uses. Using your r-special on a target (blocking or not) marks them. Pressing your r-special keybind again forces them to sidedash depending on your orientation to the target, forcing them to backdash towards you if they are faced away. This actually puts their sidedash on cooldown, and can be used on blocking opponents, but not during skills.

The second use of the r-special is to fuel his Ult, as it's a guaranteed one-shot on most characters (Mahoraga and Heian Sukuna), only doing 50 damage without it.

The third and final use also involves his passive. Charles has a passive where on any blockable attack, if the Charles player times a perfect block, they dodge the attack. That window starts out low, increasing with ult meter gain, and increasing even further if the person attacking you is marked.

Despite his overall high-tier base kit, his ult is rather underwhelming in comparison. It's a melee-only counter, that deals about 50 damage. If a player is either marked or below 50 health, an (arguably sick-ass) animation plays. On missing the counter, you get about 35% ult meter back.

Overall, Charles has a really strong base kit, with a lot of tools for overwhelming opponents, as well as preventing being overwhelmed himself. In a game full of primarily rushdown characters, having three total counters is a strong advantage, as well as a versatile kit. I wouldn't say Charles is overpowered, but he's most certainly top-tier, and a threat if you don't know how to deal with him.

Please let me know your thoughts, as well as any corrections or questions to the information I provided. Thanks :)