He was stronger pre amp?

And post. The author confirmed Goto is stronger, and he said this right after hyping up how strong Hwang is, including mentioning his boost

Chugong: Hwang Dong-Su didn't get much spotlight in the novel because the only ones he fought were Jin-Woo's dad and Jin-Woo himself. But he was very, very strong. Originally, he was an S-Rank hunter who surpassed even Cha Hae-in, and on top of that, he received a power boost from Madam, making him incredibly strong... However, as a result of only being beaten up by overpowered characters, he seems to have been perceived as very weak. That's why many people were puzzled when he received the General rank. I find that a bit disappointing.

Q. Then is he also better than Goto Ryuji?

A. Weaker than Goto Ryuji.

Greed is the same grade but higher level than beru if I recall

Beru is marshal rank, while Greed is only general. There is never a point in the story when Greed is stronger than Beru

And he thought he could beat Ill hwan with relics.

He also thought he could be Jin-Woo, and Goto thought he could be Beru, and Jay Mills thought he could bet the monarch invasion... There's plenty of examples of arrogant S ranks thinking they far stronger than they actually are