Process Hacker is a tool that can be used to identify and terminate running processes.
Process Hacker has been seen in the advanced stages of attacks, where it is used by an attacker with remote access (eg over RDP) to terminate security and logging software prior to deploying a malicious payload, often ransomware. Its unaccounted presence is a strong indication that an active, ongoing, coordinated attack is taking place.
For more information, please see the following KBA: