Despicable Me 3 is a good movie, although I prefer the first two over the third one.
The Bad: 1. Balthazar Bratt was an incredibly annoying villain, mostly because I hate Trey Parker, the man who voices the character, also the co-creater of South Park and the voice of another character I hate with a passion, Eric Cartman. I think Balthazar Bratt was partially based on Eric Cartman, which makes me hate him more than before. The moment he got defeated in the end was an awesome moment. It could be a lot worse if it had Matt Stone in the cast as well. Thankfully, this bad aspect doesn't ruin the movie as a whole. 2. It is a bit disappointing that Russell Brand as Dr Nefario did not return. He was very funny in the first two movies.
The Good: 1. The voice acting, for the most part, was really good. It consists of Steve Carell, a comedian I like, Kristin Wiig, Miranda Cosgrove, Dana Gaier, Nev Scharrel, Steve Coogan, Julie Andrews, Jenny Slate and Pierre Coffin. About Trey Parker, to his credit, his voice did fit the character of Balthazar Bratt, although his voice did make him annoying. 2. The music used in the movie was pretty good. "Bad" by Michael Jackson was really catchy. 3. The cast of characters, minus Balthazar Bratt, was likable and colourful. I love the chemistry between Gru and his twin brother, Dru, both voiced by Steve Carell. It is common to have twin siblings in animation voiced by one person. Yubaba and Zeniba, from Spirited Away, were both voiced by Mari Natsuki, as another example, albeit a foreign-language film example. 4. The animation fits the comedic tone of movie, and is pretty colourful as well.
If you enjoy the Despicable Me franchise, watch this movie, but do not expect it to live up to the first two.