The phrase "certain enemies" refers to specific or particular people who are considered to be adversaries or hostile towards someone or something. These enemies are not just random or general, but have been identified or known. Full definition
Playing for countless hours, trigger tapping to shoot the enemies as sometimes you will be overwhelmed looking for cover, switching ammo types to kill certain enemy types. (idatxbox.com)
What this also means is that certain characters have specialty abilities and weapons that are required to defeat certain enemies for example. (dailyjoystickpodcast.com)
There's a lot of strategy involved as you need to balance what tools do damage against certain enemies while also keeping the squad alive. (articles.gamerheadquarters.com)