I am not experienced in the RuneScape Universe, due to myself being in The Elder Scrolls Online Universe, since 2016, and hence I had no idea what that is, but tried searching. Apparently, it’s about the cape, and evidently this cape is almost the most powerful:
- https://oldschool.runescape.wiki/w/Fire_max_cape

The most powerful cape is, if I am not mistaken:
- https://oldschool.runescape.wiki/w/Infernal_max_cape

As of 1 March 2026, there are 37,529 players that have achieved level 99 in all skills in order to max.

Source: https://oldschool.runescape.wiki/w/Cape_of_Accomplishment