Hahahahahaha.....that logic.Because Hashi knows strength regardless and to be called a monster by Hashi is an incredible accomplishment. What attack has Tsunade used that Sakura looks like she can't use? None right? Therefore, she is Sannin level.
I know hashi knows strength but then on what basis are you comparing sakura's punch to be stronger than tsunade??
Tsunade can heal full body and did not forgot to breath against madara lol.
Tsuande without using the seal can punch as hard as sakura with seal.
Tsunade with seal destroys sakura.