The Day of the Jackal (1973)

Dry, realist, at times documentarian, but also with a dark and understated sense of humour. Leaves a lot of headroom for you to infer motives and relations. One example I liked a lot was between Lebel and his assistant Caron; the film tells you a lot from small things like how Lebel requests Caron, their first scene together setting up their operation, and the short scene where Lebel's playing solitaire while Caron does real work (but Lebel's mentoring Caron while he plays).