What is the ruling on someone who was subjected to harassment as a child, and will he enter Hellfire for that?

You are not to be blamed for the harassment incidents that occurred in childhood and after puberty, as long as you repelled the harassers and did not become complacent by being alone with them or associating with them despite knowing their ill intentions. This is based on the hadith: "Three things have been lifted from my Ummah: error, forgetfulness, and what they are coerced into." And "The pen has been lifted from three: ...and from the child until he reaches puberty." However, if there was any complacency on your part, then repentance is obligatory, along with the firm resolve not to repeat it. It is advisable to marry and avoid being alone with oneself or with those who are not trustworthy.