Trojan.Agent refers to a generic Trojan malware detection. It is used for detections that are either associated with no specific malware families or not enough information is available to pinpoint the malware family.
This is a Trojan capable of opening a backdoor on compromised machines and downloads potentially malicious files. Backdoor.ForShare is also capable of deleting user accounts and files, and monitoring user keystrokes and screens.
Malwarebytes can remove Backdoor.ForShare without further user interaction.