Gaara is no no way the weakest of the kages. I would say thats Tsunade.
1)Onoki....Maybe....He has back problems, that could lead to his defeat. He might be able to be overtaken by either of the number 2's.
2) I would say is a tie between mei and Gaara. Sure....you haters can say we know nothing about her due to it showing a minimum of her abilities. TRUE, but we CAN assume she can do far more. Reasons being:
a) There are other lava users, she's clearly the best, thought we have not seen it's max.
b) CLEARLY she can use other elements, lmao, why the **** would she only be a kage if she can only use lava, boil, and mist? Think about it.
c) I see a lot of people saying she can only use boil inside closed areas. Which is just plain stupid on their part. NO WHERE in the manga does it say that. It takes the form of mist, and as it happens, so does the hidden mist tech......Does it blow away? No. It's been shown in many different areas, at different times. The wind is not a excuse. Haters can just stfu. its obvious.
d) Gaara can't use summons, genjutsu, taijutsu, or any of that either. Also not a excuse.
Reasons why gaara is second.
a) He's just ****ing awesome.
b) Amazing sand control. He's able to control a HUGE amount, with little to no difficulty.
c)I really don't need another reason do I?
3) A....He's third because he lost a arm.....That's really brought him down. He may still have amazing speed, ect. But running around kicking won't finish the job.
4) Tsunade. Also amazing, but in her own way. She's mainly a medic. That's what she's best at. She's trained to fight in taijutsu, just like sakara. That's only a 2nd option. All the other kages also use taijutsu. She's not any better just cause she's strong.
Don't flame me just for my reasons. I have reasons behind all there placement.