Jetstream Sam is a shrug in human form. He drips with a cool factor that few characters can ever hope to achieve. He's not as much fighting for a cause he believes in, he's fighting to fight. He always seems to be one step ahead of his opponent and relishes in that fact. His laissez faire attitude shouldn't be mistaken for laziness, as he's more than willing to turn enemies into ribbons.

Sam's voice oozes brazilian swagger, with the ability to sound effortlessly cool. He's not adverse to getting serious however, and will snap into a serious mode should the situation require it.
Here's an example: https://youtu.be/aAYkdGmSe38

Feel free to take any spin on the voice you want, just try this as a base.