Oh no, I think you actually portrayed those guys like they were a menace pretty well, cause that's exactly what I thought, but I just forgot to mention it.

To make characters look more like a threat, I usually look more in depth at the colors first. What I mean by this is to use colors that are secondary, such as purple or green. If you take a look at a lot of Disney movie villains, such as Queen Grimhilde, you can see the robe she is wearing is a purple color which makes her look darker and spookier. There is also a scene in The Lion King where Scar is engulfed in a green mist, which makes the whole atmosphere ominous.

Now, colors aren't everything, you can also take a look at the atmosphere surrounding the character, like in the green mist scene I talked about earlier. Or you can make them hidden in a shadow or obstructed by an object, making the character look eerier and creepier.

You should also take a look at the face expression of the villain, making them look dangerous with exaggerated frowning eyebrows or making them smile in a sinister way. Take a look at like any Disney antagonist and you'll see what I mean.

Now, down here I'll post some links to various videos which I think will make you know more about storytelling and threatening characters in general:

1. https://www.youtube.com/watch?v=54c8svkLHf4 How to write villains;

2. https://www.youtube.com/watch?v=Ga0rs2G8BGI What makes a good villain;

3. https://venngage.com/blog/disney-villains/ Color theory about antagonists;

4. https://www.youtube.com/watch?v=EnMaMsiRfIE How to design a villain;

5. https://www.youtube.com/watch?v=PS18KPlogso How to draw a villain;

6. https://youtu.be/F-8rY-WiIt8?t=640 How to draw and portray storytelling;

   But I think you did an amazing job regardless, and next time you should try to experiment more, like with the contrast part and don't be afraid of failing! You are gonna do awesome!