I've been watching the series since around the time the Battle Tendency episodes were being uploaded onto Crunchyroll, I think. Started with Phantom Blood back then and recently finished Golden Wind. I haven't read the manga (or any manga at all for any series period, need to fix that someday) so I only know some of the things that happen in Stone Ocean, Steel Ball Run, and JoJolion from what I've read over the years on wikis or heard in videos and such. So yeah, my answers will be limited to Parts 1 through 5.
⪼
Who's your favorite character overall?
So as not to be redundant with other parts of the questionnaire, I'm going to dedicate this section to the main JoJo's.
Joseph's a strong contender, since we got to see him across three different parts at different stages of his life. His peak was obviously in Battle Tendency, since he did relatively little in Stardust Crusaders, but he was still fun to see in Stardust Crusaders, and he's partly responsible for brining Josuke into the world, so that's good despite his actions leading to that being a bit unfortunate. That moment in the pool saving Shizuka was great too.
It's neat that, as is appropriate, Giorno is sort of a mixture of Jonathan and DIO's personalities. Like Jonathan, though, his demeanor is a bit reserved compared to people like Joseph or Josuke, so he ends up coming off a bit more flat. Still a great character though.
Along the same lines as Giorno,
Josuke seems like a combination of bits of all three of his predecessors in Jonathan, Joseph, and Jotaro. Jonathan's kindness, Joseph and Jotaro's ingenuity, and Jotaro's aggression when someone irritates him. He seems like the best all-around package.
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Who's your favorite male character?
Bruno Bucciarati, Narancia Ghirga, Ghiaccio
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Who's your favorite female character?
Lisa Lisa. It's a shame she didn't get to do much fighting.
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Who's your favorite villain?
La Squadra Esecuzioni, Ghiaccio and Risotto Nero in particular.
As far as main villains go though, as much as I love DIO and just how despicable he is, my favorite would probably be Yoshikage Kira.
⪼
What is your favorite Stand?
(in alphabetical order, not preference)
Black Sabbath, Cinderella, Crazy Diamond, Cream, Gold Experience, Heaven's Door, Judgment, Metallica, Pearl Jam, Purple Haze, Sticky Fingers
If I had to narrow it down and/or pick just one, it'd be Cream, Gold Experience, and Heaven's Door at the top. Cream would probably rank first due to it's design, while Gold Experience would snag second place due to its versatility.
⪼
What season was your favorite?
Golden Wind. It's not perfect, there are things that bug me and there seems like a lot of wasted potential with certain characters, but it's the one I'm most emotionally attached to.
Diamond is Unbreakable is better in more respects and would be my second, but yeah, Golden Wind gels with me almost despite itself.
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Who is your favorite supporting character (non-main character)?
Bruno Bucciarati.
After him though, the rest of his gang.
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Who do you think is the funniest character?
Joseph Joestar, I guess. His younger self in Battle Tendency, specifically.
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Who do you think is the most underrated character?
Jonathan, I guess? Most people seem to find Phantom Blood boring by today's standards and I can totally see that being valid and can see where they're coming from. That said, I liked Phantom Blood for what it is and, while Jonathan is pretty flat and boring compared to his descendants and is sort of a relic of the past now, he was a good guy and his end was tragic.
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Who do you think is the most overrated character?
N/A
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Who do you think had the best character development?
Jean Pierre Polnareff, La Squadra Esecuzioni
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Which character do you think you relate to the best?
Little bits of Jonathan, Josuke, and Giorno. I try to be a good person like Jonathan and Josuke, though I can also have a bit of Josuke's temper. I'm pretty boring in social situations, so kind of like Jonathan being the flatest JoJo. Tying into that, I'm a bit like Giorno in temperament, more reserved.
Also, a little bit of Rohan Kishibe too. I'm hoping to be a published author in the future and can relate to his desire to be read and that being more important than the money or fame and all that. I wish I had his skill in drawing though, I have zero talent for that.
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Which character do you wish you got to see more of?
Iggy, Pannacotta Fugo, Trish Una
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Which character disappointed you the most?
Pannacotta Fugo, though at least he was apparently rectified a little bit afterward with the light novel Purple Haze Feedback. Araki didn't write it himself for what it's worth, but he did do character illustrations for it. Not strictly canon since, again, Araki didn't write it himself and there were other light novels by other authors of varying quality (Jorge Joestar is apparently quite awful), but Purple Haze Feedback appears to be the most highly regarded and doesn't seem to conflict with anything in the main plot of Vento Aureo/Golden Wind. It takes place after the end of Vento Aureo. I haven't read it myself yet, but plan to, and you might be interested too if you liked what you saw of Fugo.
Trish barely getting to do anything with
after
other than the
is also unfortunate. It seems like we could have used just a few more minor villains as part of The Boss' Unit? Speciale so we could see more of that, and maybe give Abbachio another fight.
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Here's a new question for anime viewers:
⪼ Which intro songs have been your favorite?
Mine is definitely Fighting Gold. Great Days would be my second favorite, and Sono Chi No Sadame is right behind that.
I was thinking of buying a body pillow from it, but in all honesty I haven't seen it just a LOT of interesting fanart 
