From a results perspective it's pretty undeniably 1st place Engh. Then the other big hitters would be Sliggy (liquid), NBS (Ascend), Mini (Fnatic) and Onur (Ex - KRU).
I'd also like to shout out the former immortals coaches Gunba and Packing10 who have since their start on the LA Valiant in Overwatch had an amazing eye for player scouting. (some of the top of my head, asuna, dicey, neptune, JCstani, JonahP and Genghsta in Val. aswell as KSP, Dreamer, Shax, Lastro and Rain in Overwatch league)
Coaching is really hard to judge without an inside perspective in how the team operates but all of the above have very good references from their players and other coaches, with the results to back them up.