السلام عليكم A brother has a bit of mental health issues and at times suffers from waswas, recently his head will start to hurt and get the urge to get angry at Allah but will resist diligently but for a second he may fall into the urge or get angry at Him by accident/Forgetfully. is this Kufar?

Ustadh AbdulAziz al-Haqqan
Seek out medical help for your waswas problems.