The March of the Exeggutor Squad - S1-E41
Revealing mistake: When Misty tells Melvin to be careful, her left arm passes through the stage. (00:05:13)
The March of the Exeggutor Squad - S1-E41
Revealing mistake: When Misty tells Ash to stop looking at the Exeggcute, Ash's left hand is layered over the Exeggcute. (00:09:03)
The March of the Exeggutor Squad - S1-E41
Revealing mistake: When Melvin is throwing Poké Balls, they appear out of thin air before he throws them. (00:11:42)
Answer: He is a good guy but just found himself in a bad situation when he worked for Lysander. He didn't want him to harm Ash and his Pokémon when he was trying to get the special bond between Ash and his Greninja to work. He does leave Lysander and go back to being a good person.