Janus is more likely to commit crime than Mike because Janus has a history of mania. However, if you wanted to use "most likely" you would say: Janus is most likely [in the group] to commit crime because Janus has a history of mania. An easy way to remember is more ends with the "er" sound like "greater" and most ends with "st" just like ... More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.