1. Saitama (One-Punch Man): In the world of OPM, heroes have various different abilities that range in complexity, power, and versatility. Despite the myriad of highly complex reality warping powers, the objective strongest person in this entire universe simply punches hard, runs fast, and lifts heavy.
2. Mash Burnedead (MASHLE): Very similar to Saitama. In the world of MASHLE, people are born with a "mark" on their face that grants them a specific type of magic, ranging from borderline useless (able to levitate small objects) to obscenely OP (able to manipulate, control and even erase time). And much like Saitama, Mashle is easily in the top 5 strongest people in this universe despite having 0 magic beyond superhuman strength.
3. Toji Fushiguro (Jujutsu Kaisen): Unlike the others, Toji's lack of special powers (or cursed energy in JJK) comes from a ritual performed on him as a child. Due to his Heavenly Restriction, Toji has no Cursed Technique, theoretically making him useless in a world where sorcerers have such a wide array of tools. Yet, the Restriction also enhanced Toji's speed and strength to impossible levels, to the point he was able to easily overpower Satoru Gojo and Suguru Geto during the high school years, who even then were considered "the strongest" in Jujutsu society.

In a world of complex power systems, this guy is just strong.