can detect or remove all threats.

If Hitman Pro found infection that Avast couldn't remove or detect, it is normal because not all antivirus can detect or remove all risks.

It is common for malware scanners to provide false detection especially on legitimate programs and system files but only if the files are legitimate/system files.

You need to provide us the path or location in addition to file names before we can check if it's a false detection.
Also you can send the detected threat via for online single file scan.

Note that if your system is infected with rootkit, you need to run Avast boot-time scan in order for Avast to remove it successfully. If you will only run a scan or using the avast shield (real-time protection) to remove the rootkit and other infections it is detecting, the removal of rootkit infection will not complete.