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 the generic detection for Trojans that block internet access for AV programs. This can be done to prevent the software from fetching updates or even to prevent it from checking definitions in cloud-based antiviruses.
Malwarebytes can remove Trojan.BlockAV without further user interaction. However, users are recommended to make sure that their AV is able to update after this Trojan has been removed.