BitDefender is a no go. Far too many issues. It works alright for some people but completely butchers other PCs.
You need three layers of defense. Antivirus, antimalware, and in-browser solution. While some top paid antivirus software does contain everything in one, it doesn't hurt to research.
Currently, Windows natively has its own anti-virus Windows Defender, and it works relatively well. The majority of the popular providers have free versions of their software to test out, and they also do the job. As for anti-virus, I recommend Comodo, Avast, Avira, Kaspersky or Norton. All of them proven formidable.
With anti-virus, you usually will need to run anti-malware software. Not every single anti-virus has the full package included...