1. How would you describe the personality of Pancham (as a whole specie, not certain individual kinds)? - I would describe Pancham as a species as playful and mischievous, since it is known as the Playful Pokemon and its Japanese name, Yancham, is a combination of Yancha and champion, and yancha meaning naughty. The way I see it, Pancham is mischievous in a playful way, meaning no actual harm to people and does it just for pure fun.
2. A Pancham evolves by at Level 32 if there's a Dark-type Pokemon in party, does this mean it turns bad upon evolving? Why/Why not? - Personally I'm going to say no. For two big reasons. For one, is that it retains its Fighting type. Dark is referred to Evil type in Japan, and Dark is weak to Fighting and the common interpretation is because Fighting type representing Good and Dark representing, surprise surprise, Evil. Combined I believe that it makes the Anti-Hero and it makes sense to me due to Pangoro's PokeDex entry in X and Omega Ruby, as it says "Although it possesses a violent temperament, it won't put up with bullying. It uses the leaf in its mouth to sense the movements of its enemies.". The part that makes me believe that Pangoro isn't that bad is the part where it says "it won't put up with bullying", if Pangoro truly was bad, he would either do nothing against bullying or instigate bullying. Granted it is a violent Pokemon, but at least it shows that it is not entirely bad.
3. In which aspect Pancham is better than Riolu? And in which part worse than Riolu? - There are a lot of things that I think make both equally as good as each other. Starting with Pancham, one of the few things that I think makes Pancham a lot better is its personality. Unlike Riolu, Pancham has a pretty defined personality. By asking the question, what is a Riolu's personality like, you can't really say. All you know is that it is fighting type that can sense people's emotions and it uses Aura to communicate, but what is its personality. I mean, yeah, you got natures, but that's not really a lot to go on. Pancham on the other hand has a pretty clear personality. It's playful, its mischievous, and it can't resist grinning if someone pets it on the head, and it tries its best to look intimidating and scary, but can't because it looks too cute. Another thing is that Pancham, is one of only two Pokemon that levels up by having a certain Pokemon in the party, and is the only Pokemon that only evolves by leveling up with a certain type rather than a specific Pokemon, and I personally love that as it gives the Pokemon a bit more of a personality of its evolution as mentioned before. Plus there is its name, with it being a combination of Panda and Champion, and as mentioned before, Yancha and Champion in its Japanese name. As for Riolu, Riolu is a bit more of an interesting Pokemon seeing that it can learn people's emotions through aura. I think Riolu has a better design to it and stands out more than Pancham. One last aspect of Riolu that I think is also really cool and makes it stand out more is that it is also the only Fighting type Pokemon that can have the Prankster ability.
5. Why does Riolu evolves into a part Steel-type, instead of a Fighting and Psychic-type Pokemon? - My only guess is because #ThePokemonLogicIsReal.
Which Pokemon should win the first CLASH?
Don't be shy! Tell us why! Lol - Biases aside, I am going for Pancham and for multiple reasons. First, Pancham has a base stat advantage, having 348 base stat total over Riolu's 285, and having higher attack and defense. Second, Pancham can learn a higher variety of moves. By level up, they both learn a combination of Normal, Fighting, and Dark. Riolu can learn also learn Ground, Poison, Rock, Ghost, Fire, Steel, Dragon, Ice, Electric, and Psychic moves through TMs, Breeding, and Tutoring. Pancham on the other hand can learn Ground, Poison, Rock, Ghost, Fire, Steel, Dragon, Ice, Electric, Psychic, Grass, Water, and also Flying, giving Pancham a higher type coverage than Riolu. Third is its abilities. If a Riolu and a Pancham would be put into battle, the Pancham would probably more than likely win since it has the higher base stats, and it can also have Iron Fist as an ability, giving it an attack boost to punching moves, it would surely knock a Riolu pretty fast, and pitted against other Pokemon, Pancham would still win out. Besides the type coverage and higher base stats, its abilities would guarantee it to win. Yes, Riolu can have Prankster, but Pancham can also have Scrappy or Mold Breaker, allowing it to hit Ghost Pokemon with Normal and Fighting moves, or ignore other abilities which is a bit more useful than Prankster in a lot of ways if Pancham was by itself.