Crypt0S0ul, you have to be brave enough to take this case and solve the problem. You can't force someone to admit they're guilty of an off-forum transaction between one and two other accounts. I've had a similar case where 16 accounts were involved in send all their assets in one wallet ^{[off-forum transaction],} but after they proved my suspicions wrong, I happily removed the negative tag.

I think your suspicions will be valid for determining they are alt if you can prove that they are using the same wallet or the same social media account. But if it doesn't exist, then I'm sure the existing evidence won't be enough. Again, the lesson I learned from the case I worked on was that if you can't prove all of those accounts with valid evidence have violated the campaign rules, then don't try to damage their reputation by throwing your doubts into the community. I completely gave up on the same case.