Thanos has the most amazing pair of guns!
Firstly, I have always been a big fan of the Marvel comics series. Also, Hulk has been my favourite when it comes to sheer muscle!
But this time Thanos completely crushed Hulk!
Thanos have big arms that are well developed. The sheer size and massive Biceps brachii muscle match fully with the developed Brachialis muscle. And a matching Triceps lateral head gives that 3-dimensional powerful look.
So, here are my top pick for building 3-D arms!
Triceps Lateral Head
Narrow Grip Bench Press
https://www.bodybuilding.com/exercises/close-grip-barbell-bench-press
Brachialis
Preacher Reverse Curl
https://www.bodybuilding.com/exercises/reverse-barbell-preacher-curls
Biceps brachii
Hammer Curls
https://www.bodybuilding.com/exercises/hammer-curls
Aditya