What kind of injuries would be most common for that kind of crash?
Wrong question. What kinds of injuries do you need to have your character endure?
Most common are fractured wrists and ankles. The body instinctively braces for impact and these are the two points of common breakage. Airbags are notorious for snapping wrists, as well as scrapes/burns on the arms.
Bruising is guaranteed. Face, chest, anywhere that makes hard contact. Airbags will prevent serious injuries up to a point, but at higher speeds the chest will be impacted by the steering column, crushing it and severely injuring the heart.
The body also tends to elongate during a higher speed impact. The head will contact the windshield, often snapping the neck back and causing severe neck injuries, including paralysis and death.
Most "head-on" impacts are not direct and any off-center impact will result in turning and twisting of the cars and those inside. Spinal damage is common, even with lower impact speeds. The opposing driver's reaction will almost guarantee it's not a direct collision.
Mass of vehicles involved will greatly change the dynamics. A Smart Car hitting a tractor trailer will be flattened, a Hummer hitting a golf cart might not even notice.
Condition of the driver will change the effects of injuries. Heavy intoxication will restrict the bracing reaction, allowing the limbs to bend, reducing the chance of broken bones.
So, what do you need? Or, what does your friend, who seems to be researching suicide, need? Or, do you need the number for the suicide hotline yourself?
Jeff