These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
In the original anime, Kouji Kabuto was a sexist Jerk with a Heart of Gold and a Chaste Hero. However in the original manga he was less sexist and less jerkish, but he was more of a pervert (and he even blushed when Sayaka paid him a compliment). The Gosaku Ota manga, being an adaptation of the anime, stood halfway between both characterizations. Later retellings were mostly based on his manga incarnation, but maybe his weirdest version has to be that from New Mazinger, an one-shot manga set in an alternate war-torn future where he was a soldier. As well, fans tend to argue if he did or did not love Sayaka and if he preffered Maria.
Sayaka Yumi was always a Tsundere, but in the original manga she was Type B and in the original series she was Type A. Her characterization in later versions varies between one type or another. And some fans think she was very stuck-up and bratty and more interested about showing off than saving the world, whereas other fans state she was simply an Action Girl had a very short supply of patience to deal with a loud-mouthed Idiot Hero and an aloof father.
Dr. Kabuto in the original anime and the Gosaku Ota episodes was a well-meaning, kind scientist. But in the original manga he was a Mad Scientist (and that is the version usually is followed). In the Shin Mazinger Zero manga, though, he is a Complete Monster.
Boss is the Comic Relief to some fans. To other fans he is an unsung hero who always helps to the main characters and has nothing for his efforts.
Baron Ashura usually was completely loyal to Dr. Hell. But in the Gosaku Ota episodes he got fed up with Hell punishing his/her failures and Brocken mocking him/her, and he/she decided betraying Hell.
Complete Monster (Dr. Hell worked for Hitler. Before transforming Count Brocken into a cyborg, he stated he was going to use what he had learnt by experimenting with Jews in Austchwitz. And he grinning while he told it! His lackeys are not quite innocent, either)
Ensemble Dark Horse (In a meta sense. Go Nagai originally made this simply to blow off steam while writing the horribly depressingDevilman manga and directing the anime. Mazinger blew Devilman out of the water in terms of popularity, which Nagai always had odd feelings about.)
Germans Love David Hasselhoff (The Spanish loved it so much that they built a statue. No really. To be fair, it was going to be a part of an amusement park that was never built, but still...)
Harsher in Hindsight: In episode 17, Holzon V3 unleashed a chain of strong earthquakes left in ruins several Japanese cities and killed a lot of people. Forty years later, after a chain of earthquakes and tsunamis turned several Japanese cities in rubble, that episode looks even more tragic.
OT 3: There are not many fans who do this, but some of them consider Kouji/Sayaka/Maria is a solution to the most important Love Triangle in the trilogy (nobody seems considering Kouji/Sayaka/Boss or Tetsuya/Jun/Boss, nevertheless. Poor Boss).
It is lampshaded in this Super Robot Wars Yonkoma comic: [1]◊
In fact, that characterization was more in line with his personality in the original manga.
What Do You Mean, It's for Kids?: Right like many Go Nagai works, Mazinger Z was aimed to children and young teens in Japan, but it was judged to be too violent to be seen by children in other countries like Spain and Philippines.
