Hi, In my opinion, bat will be the most closely related to hawk.
Why?
This is because, when we consider the photo of a bat and a hawk, we notice the similarities like:-
• Wings- They have nearly the same short wings decreasing the area of contact with air and enabling higher flight area.
• Presence of small snouted beak-like structure and presence of less or more similar color.
• Both live in trees and are normally not companiable with humans.
• Hawks and bats are both having a similar anatomy, not body, I meant that they have similar positioning of organs like stomach, pancreas etc.
• They have the sense of locating prey miles away, enabling easier locating of food.
Hope this helps...
{ Answered by Benjemin }