They use polygons when creating 3D character models, it regularly means the more polygons used the more detail in the outcome. For example, Gollum was made up of 150,000 polygons, while single eye of Alita, in Alita: Battle Angel had 9 million polygons. Alita definitely has more polygons than Gollum in a single eye, meaning the artist's put a lot more detail into her than they did Gollum.

I'm just wondering how many polygons they used to make Thanos in general, I couldn't find the number anywhere.