Blackmail is blackmail is blackmail, there is no difference in severity when it comes to a situation like that.
With scamming you could easily describe severity through amount scammed, number of people scammed, number of times evaded to scam, and others. But you need not mention how they scammed, who they scammed, etc.
With scamming I see where you are coming from, but still, who they scammed could be a large factor. If they were scamming newcomers then they are more of a threat than if they were scamming trusted members, as the newcomers are more likely to fall for the scam tricks. The method also could matter, as if they scammed via a lure/social engineer/teamviewer it could give an idea to how determined they were, and how planned it was, or if it was a spur of the moment un meditated scam.
Blackmail does have different severities, from a number of situations
A) Give me x or I get you banned on sythe (really serious, most likely deserved)
B) Give me x or I ddos you (6 month ban minimum)
C) Give me x or I get you a TWC
D) I have information that you need, I'd trade for this and keep pushing until they do for an amount that you desire.
The sythe ban/twc are serious for the person getting blackmailed, as if they did have a good reason to ban them, they will obviously pay it. However, it would also benefit sythe as he could take the goods, and with them he would technically blackmailed, but he could also use them to counter-scam and repay the people he scammed when evading etc. IK counter-scamming is a grey area tbh, as it's allowed in certain situations but not others, this could get messy. Either way, there is a limit to how much normal members could find out without it being leaked information, and that could lead us to have irrational decisions. If there was a section for this, there should be a minimum post count.