The phrase "boss battles" refers to the final and most challenging fights in a video game level or stage, where players face off against a powerful and difficult enemy, often a main antagonist or a major adversary. Full definition
There are a fairly large number of boss battles in the game, and almost none of them pose any kind of challenge to your characters. (riddlethos.com)
The freedom to experiment brings to life a variety of boss battles with new creatures, many of which still subscribe to the series staple of three hits leading to victory. (gamesugar.net)
It's also possible to purchase health items and revive oneself if defeated in boss battles with premium currency. (adweek.com)