"Boss characters" refers to powerful and challenging enemies or opponents in video games or fictional stories. They often appear at the end of a level or game, and players need to defeat them to progress further. Full definition
The collection set will also include the «X Challenge» mode where you as the player will fight against a mixture of boss characters from all eight Mega Man X games. (catwithmonocle.com)
As battles, especially against boss characters, can drag on for quite some time, you'll generate plenty of this disposable resource. (selectbutton.com)
The original eight world warriors are back, along with four playable boss characters and four newcomers to this version of the game. (nintendotoday.com)