Had one of the most badly infected computers I have ever had. Client wasn't sure where this came from but could have been an attachment to an email from someone he knew who he found out later didn't send it.
System was Intel 6700K with 500 gb Ssd drive and 16 gb 2133 Ddr3 ram moving like a snail. Most of the desktop items would not open to right or left click. Classic Shell start menu gone and Win 10 start menu would flash quickly then go away if open too long. I tried to run Hitman Pro Kickstart from usb but would not run. I could boot to it but would show up failed with any choice. I fought hard and finally managed to open a score of rkill programs and picked back some speed and was able to run some scans. Rogue Killer removed 7 Trojans but system began to slow down. Hitman Pro found next to nothing, Malwarebytes MBar rootkit scan found nothing as did Malwarebytes which was also onboard as pro version along with WD as only defenses. Adw Cleaner pulled a few as did JRT but nothing much. Zemana found nothing and of course Combofix will not run in Windows 10. I kept having to rerun rkill versions when system would begin to slow again. Each time I would access my flash disk I had to go in another way because the last way in was blocked next time. So I decided it was a losing battle and manged to get into System Reset which beautifully restored Win 10 to day 1 with the files and data in tact I simply had to reinstall programs. PC Setup, Recovery and Update,Recovery, Reset Pc and you can choose with or without current files. It took about 1 hour to complete. I forgot to mention System Restore had only 1 restore point which was of no use and I noted System Restore defaulted to 250 Meg which is really stupid.
I never knew what was in there but whatever it was I have never seen such a powerful virus basically that nothing could touch and I have been doing this 15 + years.