It was mention a lot of times in the past,complete arsenal has every power,except things like omnipotence,but still has all powers.

But Cosmic Otherness is different right? Right?

yes, but ajimu najimi (the greatest example of complete arsenal) is literally different from any fictional character, because she literally has so many skills and powers.

that if you nerf her or buff her,it wouldn't make any difference,because of her unknown nature and meta.

Literraly,vsbw decided that she will not fight,not because she is tier 0(making this clear)but because all of her skills are unkown and every sound NLF,but is weird not using all of her skills,so they decided that she will not fight,even if is ridiculous.

Complete Arsenal being a expression of omnipotence would also have every single power, known and unknown, including Cosmic Otherness. Based on this reasoning there could be something more powerful than Cosmic Otherness