User blog comment:Crimson Storm Mich/Future Units Preview v2/@comment-26944381-20170529221617/@comment-27628307-20170603060230

IMO, the best critical booster in Global is currently Sakura Miku, and also in Japan as well if ever she was released there. While 100% crit buff is also available on Kyle, he's only a 6* unit.

You also need a best healer, and I nominate Rinasella for that.