I believe Jiraiya is a little underestimated here.
Jiraiya vs Killer Bee Bee wins with Mid-High Difficulty
Jiraiya vs MU Jiraiya wins with Mid-High Difficulty
Jiraiya vs 2nd Mizukage Jiraiya wins with Mid - High Difficulty
Jiraiya vs 3rd Raikage. Jiraiya wins with High Difficulty
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Jiraiya vs Killer Bee
Jiraiya: Alright Jiraiya is an impressive Ninjutsu and Taijutsu specialist. He posses the ability to turn anyone he touches into a toad, he can summon all the toads from Mount Myoboku including Ma & Pa. He posses the elements of Fire and Earth, where he has shown impressive feats with each element, creating a swamp large enough to sink an enormous snake, while he was in a weakened state. His fire is so powerful he could finish off a summon in a single strike. Jiraiya is also capable of accomplishing impressive feat with his taijutsu, as he took down one of Peins summons just using a single round house kick. Jiraiya is incredible intelligent and won't rush into battle, he is very proficient with clones and he is a master of espionage and infiltration, meaning he is very skilled in hiding his presence. Lastly his most powerful arsenal is his Sage Mode. In this mode he unlocks a vast amount of energy and power being capable of performing an enormous rasengan capable of destroying a mountain, also his speed and strength is drastically increased as seen when he literally dissappeared and reappeared right behind pein in the middle of battle. His Senjutsu is very impressive, and he can still perform impressive jutsu including the Senpo Goemon creating a vast sea of boiling oil almost impossible to dodge. Also he can perform simple Toad jutsu such as toad mouth binding and he can send a person into a toads belly without touching them. While in Sage Mode he has Ma & Pa on his shoulders which gives him two other pair of eyes helping him, and if it wasn't enough the two toads are sages too with impressive speed and strength, being also capable of a sound genjutsu so powerful that it put pein under it within a short period of time.
In short, Jiraiya is no shinobi to take lightly in any battle.
Killer Bee: The Jinchuriki of the Hachibi. He is a master of Kenjutsu to such an extend that he could easily handle Sasue Uchiha with his seven blades while Sasuke had his 3 Tomoe activated as he could not follow Bee's movement and was stabbed several times while Bee suffered no injuries at all. Besides this, Bee posseses a massive amount of chakra and strength being able to chop a persons head off with his bare arm. He is a master of raiton and utilizes it with his sword style and his body increasing speed. strength and durability. His also posses one of the seven swordsmens swords, the Samehada, which can absorb an enemy's chakra or attack leaving it very difficult to attack the wielder, though the downside of Samehada is it has it's own personality. Samehada cannot handle Natural Energy. Killer Bee's ultimate weapon is the Hachibi, he gains unbelievable speed and strength being able to fight many powerful shinobi equally as he posses the full power of the 8 tails.
Conclusion to this fight: This fight would be impressive as neither of the two sides would rush into battle, they are both intelligent, Jiraiya being a pervert, Killer Bee being a rapper. They both analyse their situation seemingly fast and precise, they both posses very strong abilities and Killer Bee as we know him would not enter the 8 Tails immediately and even if Killer Bee did so, it would be a difficult battle against Jiraiya and the Toads. If/When Jiraiya enters Sage Mode, Samehada would be impossible to use and 8 tails full mode would be slow compared to him, though the Hachibi, though if Killer Bee uses his incomplete mode he will gain massive speed and the fight would be very interesting.
In my eyes this fight could go either way but I think Killer Bee has the edge over Jiraiya due to his large stamina and raw power with the Hachibi, but if the Hachibi is taken out of the equation, Jiraiya would win.
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Jiraiya vs Muu
Muu: Muu is an impressive warrior who is capable of flying, becoming invisible even to sensor, though he does not erase his body but simply turns invisible (this feat is stopped by Jiraiya using his barrier technique which detects movement inside it). Muu is also capable of performing Dust Release which is incredible powerful while he is also very fast. Muu is a powerful warrior who taught Oonoki everything he knew and met Madara in battle.
Conclusion: As to what I have seen from Muu and Jiraiya there is no question that Jiraiya would take this battle. Jiraiya would simply need to use his barrier for Muu being unable to go invisible and Jiraiya would easily fight his speed and flying by using the toad techniques and sumon Gamaken/Gamabunta who can jump and dash around with impressive speed. while also the Dust Release is created in the users hands then shot at the opponent and is dodgeable, and if caught, Jiraiya can simply use reverse summon to Mount Myoboku or inside a toad then return to the field. Jiraiya wins this with Mid - High diff.
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Jiraiya vs 2nd Mizukage
2nd Mizukage: Mizukage is very powerful being able to summon a giant clam, using a almighty genjutsu which is dodgeable. The Mizukage can utlizie water jutsu and his Steaming Danger Tyranny. Despite these impressive powers, I just don't see how the Mizukage can keep up with Jiraiya's summons, Fire/Earth, Toad techniques and Sage Mode.
Conclusion: Jiraiya wins U_U
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Jiraiya vs 3rd Raikage
3rd Raikage: The 3rd Raikage has impressive feat, defeating 10.000 shinobi and defeating the Hachibi. He has immense raw power and speed, he is a true master of lightning gaining unbelievable speed and strength while also possesing the Black Lightning.
Conclusion: Despite the Raw power and speed of the Raikage and his black lightning i do believe that the Raikage will lose this battle, as Jiraiya has just a larger arsenal and he is still quite fast and would not go easy and his summons, toads, techniques would overwhelm the Raikage being able to summon 3 giant toads and Ma & Pa. He can turn the raikage into a toad on contact if get the chance, he can use sound genjutsu to stop him and even in sage mode he has impressive speed and power too. Jiraiya wins with High diff.
