There needs to be an option to report people that go after the players losing or that have no chance for their own personal entertainment. I just played a a game where I had 3 points and the players ahead of me had 11 and 12 and continued to trade together, block and rob me, and then tell me in chat it was so much fun to do it. I paid money and shouldn't have to play with people like this.
All you can do is add them to the blocked list. I do get them scunmbags as well time to time. Shame on them as they do it blatantly to harvest ELO by securing first 2 position in a 3 player game.
Some people are just spineless.
In a game right now where one player keeps giving another all his cards then bragging about it. Both should be banned, but the admins never do anything about these people.
Use the in-game report feature. It sends complete game and chat logs and has a comment section so you can highlight the behavior you are reporting.