While Apex Legends does have anti-cheat in place, it is not always enough to stop people from cheating. Although it does a good enough job to keep people from cheating, it is not a perfect system as things like strikepacks exist.
A strikepack is a device that players can put on their controller to pull the trigger at speeds that shouldn't be possible, meaning players who use this on single-fire weapons would get ridiculously high TTK without triggering the anti-cheat that Respawn Entertainment has in place.
A Redditor by the name of Nervous_Difficulty_6 posted a clip showing off an enemy Wraith using the R-301 Carbine in single-fire mode while shooting fast enough to be confused for being in full auto mode.
The enemy Wraith showed no signs of recoil when firing their weapon either, meaning some form of strikepack was being used behind the scenes. While the enemy Wraith was clearly cheating, players from all over the internet came together to mock the cheater for their poor gameplay and game sense. Players also made mention that despite shooting quickly in single-fire mode, switching to full auto while taking close-range fights would have been an easier way to take those fights.
While this particular cheater was ridiculed on the internet, many people still feel that Respawn should do more to limit the ways that players can cheat in Apex Legends.