You've install the Antivirus One app. It is not needed. You have Malwarebytes installed and that is more than enough to protect you from malware and adware. Uninstall Antivirus One according to the developer's instructions.
Give this a try: boot into Safe Mode according to How to use safe mode on your Mac and reboot normally. Then try rebuilding the Spotight index again.
NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following;
• Verifies your startup disk and attempts to repair directory issues, if needed
• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)
• Prevents Startup Items and Login Items from opening automatically
• Disables user-installed fonts
• Deletes font caches, kernel cache, and other system cache files
NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.
