Microsoft Defender. 3rd party antiviruses are bloatware with tons of useless modules - cleaners, shredders, extensions, password managers, vpns, driver updaters, software updaters, optimizations etc. 99% of OS and app crashes, bsods, slowdowns etc are related to 3rd party antivirus apps or optimization apps etc. Almost impossible to completely uninstall. Sometimes only a clean Windows reinstall solves the problems. You should listen to what the best cybersecurity experts says, not some random youtubers and pseudo experts.
Tavis Ormandy:
I get asked constantly what av to use. You're missing the point; av creates more problems than it solves, and we're overdue an av slammer.
Justin Schuh:
AV products poison the software ecosystem because their invasive and poorly-implemented code makes it difficult for browser vendors and other developers to improve their own security.