Answer:
Macbeth's act of murdering Duncan, Banquo, and trying to kill Banquo's son make him a terrible king.
Some people remained loyal to Macbeth because they knew that after Duncan, Macbeth would be the next king, and they do not want to be disfavored in the eyes their king.
Explanation:
"Macbeth" is a tragic play penned by William Shakespeare.
Shakespeare has characterized the character of Macbeth which is driven by ambition and lust for power. In his pursuit of his ambition of becoming the King of Scotland, he make his sinister plans come real, by murdering King Duncan, to steal his throne. When the guards witnessed murder, he killed them too. And, when Macbeth became suspicious of Banquo he killed him as well. He actions of murdering and coveting the throne of Scotland made him a terrible king.
In the play, some people remained loyal to Macbeth, even after knowing his sinister actions such as Seyton. They remained loyal to Macbeth because they knew that he will be the next to be enthroned on Scotland's throne, and if they would become disloyal to him, their lives would also be in danger. They feared, that if, Macbeth can kill his dear friend Banquo for throne, than their lives can also be in danger if they would be disloyal to him.