Companies around the world are on a shopping spree. Buoyed by years of sustained economic growth and low cost of debt, global appetite for mergers and acquisitions (M&As) is at a 10-year peak despite the simmering trade war between the United States and China. Last year, announced transaction volumes surged to $4.1 trillion, the third highest ever. Yet M&As also have a depressingly high failure rate of about 80%. Combine the buying frenzy with the post-deal outlook and you would have cause to ask: which M&As have the best odds of success?