one of my colleagues is difficult to deal with
My colleague is very difficult to deal with. I was recently provided the task of managing my colleagues and it is very difficult to gain their attention and ask to fulfil a task as they do not like being assigned tasks from my end. Often they find it easy to assign the blame and neglect the task being assigned by me. My post is not official but the task of managing is real and is being carried out and there is literally no concern from anyone except this one guy who is supposed to be my friend.
Frame challenge: You're difficult to deal with, not your colleague. (I'm assuming. Don't have enough details to see the whole picture, so this answer is a stab in the dark.)
If I were in your colleague's shoes, with you coming in to manage me (without my input, and apparently even without an official position granting that authority), and then you decide to start imposing management techniques top-down onto me, without any of my input... I'd be pretty annoyed.
Top-down assignment specifically is one of my biggest peeves. The moment I read:
they do not like being assigned tasks from my end
I though "Yeah... neither would I." What problem are you actually trying to solve, by assigning tasks to them rather than telling the team as a whole what needs to be done and letting them self-assign?
- Throw away everything you assume you know about what managing a team means.
- Talk to the team to learn from them the biggest pain points.
- Talk to the team to tell them what the overall goals are.
- Talk to the team to collaboratively estimate the biggest roadblocks to reaching those goals.
- Talk to the team to collaboratively come up with possible solutions.
- Go from there.