Why was Ronan so tough? I don’t really know much about the Kree but i assume they are not supposed to be super beings able to shrug off direct missile hits or their war with Xandar would have been over pretty quickly. I would have guessed it was the infinity gem giving him super human strength and toughness but he wrecked Drax before he ever got it and he was single handedly giving the entire Xandar forces trouble before the start of the movie. Is he some sort of super Kree?
Comic version at least:
If DC wants to do a crossover, his “exhaustive knowledge of the legal code of the Kree Empire” may prove useful in the legal case of Batman v. Superman. 
One might argue that comic characters who have names have extra powers by default over random schmuck. Plus “Accuser” = a job with lots of resources.
As far as the movie goes, it’s not explained. And I don’t think anyone cared. 
This was actually my biggest beef with the movie - I don’t think they did a good job building up Ronan as a threat. He has one scene where he physically fights Drax and that’s it (and it’s somewhat of an awkward scene). I think they needed a more physically imposing actor and more/better scenes that really show that Ronan is more on par with someone like, say, Thor. Since, as you say, there’s nothing else to make us think that the Kree aren’t just different-colored humans.
I agree, and I know the comics. It’s almost as if he were a MacGuffin chasing an Eucatastrophe. He’s powerful and menacing because others (Nova Prime and the Broker especially) say he’s powerful and menacing. Killing some random Chitari isn’t much - Black Widow did the same. You can get by without showing power by showing menace, but they really didn’t give Lee Pace the time with so much going on. And let’s be honest - it’s the villains who make superhero movies really click. Thor and Avengers worked because Loki was so good. Thor II had Malekith who, as written, was nothing other than a cardboard cutout of a villain, and the movie suffered for it.
That said, it’s hard (not impossible, but really damn hard) to find more physically imposing actors than Bautista.
Dwayne Johnson The Accuser!
Last I heard, The Rock is going to be Black Adam or Captain Marvel for the Distinguished Competition. Not that it rules out working for both (said Ryan Reynolds).
And, of course, Daredevil is the new Batman.
Honestly, Marvel’s films have rarely focused around a strong villain - and some arguably didn’t even have a villain.
They don’t focus around the strong villain the way the Dark Knight trilogy did, but the villain still makes the hero in the Marvel movies, with maybe the exception of Iron Man. It’s hard to do a good superhero movie without a strong villain (and I don’t mean the villain’s power level).
I could see feeling let down by GotG with Ronan as the main nemesis if all the viewer knows comes from the movie. I’m a big GotG fan, going way WAY back, and I’m a huge Thanos fan who’s wishing they get him right, so I can fill in the blanks, so I was more satisfied.
The villain often makes the story, but not always. In GotG, the real heart of the movie was the five (or six, counting Yondu) protagonists’ relationships with each other. Their relationship with the villain is secondary to that, which means it makes sense to use a stock villain who doesn’t need much development.
I think we’re pretty close. I think the film was saved because of the development of the protagonists’ relationships despite the stock villain.
That said, when they make the inevitable sequel, they’re going to need a stronger villain, to mix things up with the now-established team.
I was listening to the Director’s commentary the other night, and he was apparently really pleased when Bautista came in to audition, because they were having trouble finding an actor who could look imposing next to Chris Pratt.