Complex sentence: Léo also depends upon tips from shady persons and many times he trusts criminals in order to achieve his goals, on the other side Denis Klein is the figure of an accomplished police officer but with a dirty attitude and questionable ethics.
Split into simpler sentences: Léo also depends upon tips from shady persons and frequently trusts criminals in order to achieve his goals. On the other hand, Denis Klein is the figure of an accomplished police officer, but with a dirty attitude and questionable ethics.