If the protagonist never struggles in the anime or manga, it is usually because he is overpowered in the very explicit way - has powers no one has, operates on the different scale than everyone else, etc.
Struggle often isn't the point.
In western web novels, the protagonist is de facto overpowered, but not explicitly overpowered - he isn't technically supposed to have all the powers, but he is so competent and genre savvy that all challenges are negated before they occur. The protagonist is supposed to struggle, in theory, but never does in practice, because he is "smart".
There is the point in the story having no struggle.
If you compare it to the game ...
- the conventional protagonist learns from failures again and again
- the anime protagonist starts with the end game statistics and items
- web novel protagonist already read the manual / guide and is recording the perfect play through