Agastya at this point does need medical help...
Yes he has done a lot sins and they were all creepy and scary as hell and its tough not hating him after that...But so far it has been shown its all due to him not being mentally normal, this obsession for Pakhi its basically a part of a mental condition that his dadi should have gotten help for and his bad acts are due to that...unlike the other IMMJs bad main characters, Agastya is sick not evil...it may not make sense seeing his deeds but in his good moments it shows that he is not beyond help...
characters psycho like him, they should either die or get treated and become better...jail is so not an option for clever psychos like him....that will only make situation worse as he will eventually get out somehow and become worse...for the sake of pakhi, No jail is not an option...
Pakhi doesnt need to actually stop hating him, but if she is not gonna let him die somehow then she better atleast start acting like an ally and get him to seek medical help...sabki bhalai isimein hai...making him go to jail wont help anyone, a guy like Agastya wont be stopped by the law...