Which program can I use to design / draw pc / ps4 game characters?

A friend of mine is programming a PC game and asked if I can draw / design the characters for him. Unfortunately, I have no idea with which program I should do this.

[it does not necessarily have to be a simple "foolproof" program, moreover, the characters should be designed in great detail]

For 3d games you need 3d modeling programs like blender or maya, for 2d you can use photoshop, or actually as good as any (even free) image editing program (eg, krita, sai, medibang, etc)

Does he want to integrate the characters directly into the game, or should you simply draw a concept / design?

Because if the latter is true you could also traditionally, for example, work with watercolor, if you feel comfortable with it. If it were necessary to digitize the pictures, you could simply scan them or take pictures.

A character design does not necessarily have to be created digitally. If you still want to work on the computer, you should bear in mind that it will probably be difficult if you do not have an iPad or graphic tablet, because working with the mouse is not very pleasant in my opinion.

But you do not need to buy something in that direction when you're just starting out. Then it probably makes sense to use a free program first to familiarize yourself with drawing on the computer.

Here are some free programs you could use:

Gimp
Krita
MyPaint
Corel Painter

Unfortunately, I did not try it myself, because I started to work with Photoshop relatively early and you are also limited with a Mac again with the selection of programs.

Drawing or modeling - ie 2D or 3D?