Level 1 with S-rank Drop Rate is the Strongest summary:

Satou Ryouta who died from overworking at a black company was reincarnated to another world. Although Ryouta was alive, he is now burdened with the inconvenience that his level is fixed to 1 in this new world.

Although he wasn’t able to raise his level, he had a unique skill that can create a cheat-like item that shouldn’t exist in the world from a monster.

He got to know about his status and MAX them with the help of ability-up items. He gathered a number of weapons and items that can only be used by himself, allowing him to be level 1 but yet, having the strongest equipment.