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.
Trojan.BlockAV is the generic detection for Trojans that block internet access for Anti-Virus programs on Windows systems.
Trojan.BlockAV hinders the online operation of security software. This can be done to prevent the software from fetching updates or even to prevent it from checking definitions in cloud-based antiviruses.
Malwarebytes protects users from Trojan.BlockAV by using real-time protection.
Malwarebytes can detect and remove Trojan.BlockAV without further user interaction.