What is the punishment for looking at a women naked without their consent?How to ask for forgiveness?Should forgiveness be asked from both god and the women offended? What to do if u are afraid to reveal the transgression to the women as it will cause problems? What if the age of the transgressor is between 16-18?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad, sallallaahu`alayhi wa sallam, is His slave and Messenger.

As for worldly punishment, your hidden faults might be unveiled to others in the same way you unveiled the hidden faults of other people. This is based on the Sharee'ah rule indicating that “one reaps what he sows". In his Ghidhaa’ Al-Albaab Fi Sharh Mandhoomat Al-Adaab, As-Safaareeni Al-Hanbali said, "Ibn Maajah reported a Hadith with a good chain of transmission on the authority of Ibn ʿAbbaas that the Messenger of Allah said, “Whoever conceals the (hidden) fault of his Muslim brother, Allah will conceal his faults on the Day of Resurrection. Whoever exposes the fault of his Muslim brother, Allah will expose his faults, until (so that) He shames him, due to it, in his (own) house.'” In his Al-Adaab Al-Kubraa, Imam Ibn Muflih  said, “One righteous man once said, 'I did not lower my gaze at a certain woman, so I was afflicted with some people not lowering their gaze at my wife.”

As for the penalty in the Hereafter, Allah is the One Who knows best.

As for the way how to repent from this sin, it is duly fulfilled through showing remorse for doing it and determination not to do it in the future. You are not obliged to tell that woman about the incident, since this might bring about evil. It is rather sufficient for you to make sincere repentance to Allah, the Exalted, and to much invoke Him, The Almighty, to forgive you. As for the point of asking a wronged person to forgive a sinner for violating his incorporeal rights, it is a matter of dispute among Muslim scholars, especially if the wronged knew nothing about the violation of these rights and there was an possibility for bringing about enmity due to that. So, the opinion we rely on in issuing Fatwas is that the sinner must not seek the forgiveness of the wronged under such cases of violating incorporeal rights, rather he has to make sincere repentance to Allah, the Exalted.

As for the age recorded in question, the person at that age is Mukallaf (i.e. legally competent, obligated person), and thus would be held accountable for his deeds and should make repentance, for whomever sincerely repents to Allah, He would accept his repentance and pardon him.

Allah knows best.