My recommendation is Comodo. I haven't noticed it slowly my computers down except during updates.

I question whether Malwarebytes finds anything, ever; anyway, it's meant as a backup to regular anti-malware defense. Avast was a headache when I used it years ago. McAfee's and Norton's free products have cost me replacement hard drives and are no longer allowed on my devices. Windows default options on 10 aren't bad, though I trust the firewall more than the anti-malware.

General advice to whoever reading who wants it: Whatever you use to find and root out malware, make sure to also use a firewall at all times. A firewall is like your body's skin, blocking access to dangerous organisms, while anti-malware is like your body's internal immune system. You don't want two immune systems watching the same area all the time, but you and computers need layered protection. The firewall can be same product package as anti-malware (like on the Windows 10 OP) or can be separate.