3) He Hates Captain Boomerang
As you would expect for a team comprised of supervillains, rivalries abound in the Suicide Squad. But none is stronger than that between Deadshot and Captain Boomerang.
Apart from both being naturals with their very different choice of weapons, Lawton and Digger Harkness are completely different in terms of personality. As we now know, Deadshot is the serious type and likes to get the job done with maximum efficiency. Boomerang, on the other hand, likes to kid around and thoroughly enjoys being a villain. While Deadshot is a bad guy because of past trauma, Harkness is a bad guy because, well, he’s a bad guy.
Presumably this will be at least alluded to in Suicide Squad, as Jai Courtney’s comedic take on the character does seem to be very different to Smith’s more sombre Deadshot.