What extension? Have you tried uninstalling Chrome altogether and using an alternate browser?
From another PC, download a rescue CD (off-line scanner) like the ones below. Boot from that CD/USB drive and scan your system. Remove all identified threats.
https://www.majorgeeks.com/files/details/avg_rescue_cd_(for_cd_creation).html
https://www.bitdefender.com/support/how-to-create-a-bitdefender-rescue-cd-627.html
https://support.kaspersky.com/viruses/krd18
However, you may have to perform a full, clean install to destroy the infestation. Hopefully, you have a back up of your files somewhere.