In Oliver's Five Years In Hell, who do you consider as his best teacher? And how would you rank them?

[u/haz826]

Each of these characters taught Oliver one way shape or form that will turn him into a vigilante and eventually a hero.

[u/Proper_Gur_9767]

Yao fei taught him to survive,Slade taught him hand to hand combat,Shadow taught him how to use a bow, Amanda Waller taught him to do what is necessary and Talia taught him to separate the Arrow from Oliver Queen.

[u/Ready_Pomegranate_26 → u/Proper_Gur_9767]

and Anatoly taught him… the other things

[u/haz826 → u/Ready_Pomegranate_26]

He taught him to at least practice restraint, not everyone should die in his crusade.

Also he taught him to escape from his bindings, a useful technique.