Congratulations. You have just shown you have absolutely no insight whatsoever in OP if you say that BB is weak =/
1: BB inflicted the scar on Shanks eye even before he had a devil fruit power. He was someone even Shanks recognized as a powerful foe.
2: He killed Thatch, WB 4th division commander. With other words someone who's stronger than Vista, one of the strongest swordsman in the world, a person who even Mihawk acknowledged.
3: He has knowledge about haki.
4: His Yami fruit allows him to negate DF powers and to absorb anyone and anything in it and to throw them back out.
5: His Quake fruit allows him to pretty much destroy everything
6: He beat Ace, WB 2nd division commander.
7: He's extremely tough. He survived a direct attack of WB Bisento and his Quake Fist. Also he didn't receive much damage from his fight with Ace. On top of that he also took Sengoku's shockwave head on.
8: He beat the crap out of Jewelry Bonny, one of the Supernova's. I wouldn't call her that powerful, nonetheless she was worth over a 100M and she was nothing compared to him.
That guy is one of the strongest, if not the strongest, characters atm. He would be easily beat by someone like Zoro? Be real, even I wouldn't say something like that and Zoro is my favourite character. Read the manga. Saying that BB is weak isn't even an opinion anymore, that's just a complete lie. He has been hit a few times by a variety of characters, however he always stood up after it without any problems and those hits were more the result of his laid-back personality than anything else.