What should I do if I feel bad about weak academics?
No need to bother much. You have thousands of inspirational personalities who miserably failed in academics but have reached greater heights, almost in every walks of life. Stay cool and focus on your career. Practically it is impossible to go back, appear for the exams and generate new results. Weak academics is generally due to lack of attention towards studies, improper guidance, limitations of the institutions where we have studied etc. It is an unfortunate thing which happens with most of us.
You don’t have to feel bad about weak academics. A bad phase is over. Now you can use your skills, strengths to shine in your professional career. Best of luck.