The following algorithm is used for elimination in round-robin tournaments:
1. If a player has played less than half of the matches, all results of their matches are annulled.
2. If a player has played half or more of the matches, they receive a technical win in all remaining matches, and their remaining opponents receive a technical loss. The results of already (actually) played matches are not revised. Technical results carry the same weight as real results.
This is the only normal elimination algorithm in round-robin tournaments; I personally tested it in previous Crusades.