Encourage your candidate to ask employees or colleagues for 360º feedback. How do they assess his ability to cooperate? What are they optimistic about and what do they think could be improved? Discuss the report with your candidate.
Investigate with your candidate what is keeping him from working with others effectively.
Encourage your candidate to practise in a role play communicating with the ‘type’ of a person he does not like.
Set your candidate certain difficulties in a role play (“this cannot happen; you cannot do this; this does not work like this”) and encourage him to deal with these problems strategically.
Evaluate with your candidate what is keeping him from being flexible when working with others.