There are several services that will do the heavy lifting for you if you’re owed compensation, in exchange for a percentage of the proceeds. Many customers can’t be bothered to deal with compensation on their own, or fight for it when an airline first denies a claim.
One such company is AirHelp, and they have their own ranking of airlines based one third each on on-time performance, their rating of service quality, and how good the airline is at honoring compensation claims.