Okay,
1) gaara vs A.
A dosent start in raiton armur,he starts in base,so blitzing in the first second isnt a problem.
Gaara himself,reacts to explosins the nstant they explode,
look at this
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then
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there was no sand when that bomb blew up,but ther was sand theee the next panel,that proves that he can block spilt second attacks,like A's shushin.
He knows hpw fast A is,A isnt ramming through his sand at all,a susnanoo sword,nor 5 could kill hm when his back was turned,so the force of A's mpact woild do nothing.
Gaara can take flight and then the fight is over,gaara has already blocked a v2 strile from A,in which je also blocked an enton spike from below from sasuke at the same time with just a little sand stream and neither touched the other at all,A dosent posses enough force to breach his defence.
Speed being a weakness for gaara is based on part 1 versions,which hold no water anymore,as blcoking explosions the nstant they explode,reacting to a forest,and reacting to rising spikes of bones when he was 13 proves that speed is no longer a problem. A dodges what he sees,gaara atacks from all angles,and can do this
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sand hail also beats A.
2) gaara vs onoki:
onoki's old age and fighting style will be his downfall,he is required to stay still and take a few seca tp prepare the jinton.gaara would be on his tail through out the fight,gaara also said he was faster than onoki when flying. Onoki's rock golems would onl allow gaara to make more sand from them,thus simultaneusly incresing his sand range while decreasing onoki's,his chakra is also ,much higher than onoki's and thus can go far longer.
Gaara vs tsunade:
a taijutsu fighter of decent speed wont get close to gaara,not much is needed to be said.a sand burial or prison sand burial ends the fight
gaara vs mei:
mei has no good defene,acid nor larva are hurting gaara who can fly over them,sand offin or sand hail kills her