Why didn't Harry feel the pain when Voldemort used the Cruciatus Curse to ipakita everyone he's dead?

It is the same as with Lily: she died to protect Harry and therefor Voldemort could not hurt him. (Voldemort undid that sa pamamagitan ng taking Harry's blood in order to return).
Harry died to protect others and therefor Voldemort powers was weakened, though not eradicated. (that's also the reason why the pertrificus totalus did not hold on Neville and the silence spells did not hold on the crowd of Hogwartians.)

cuz when voldemort killed harry he killed the last horcrux so there 4 ultimately makeing his powers week

i think 'coz he had died, he had learnt how to be (mmm how to say it?) out of his body so he achived not to feel pain.. i don't know if u understand wat i mean..

I think the body of harry had started forming a sort of immune against unforgivable curses.Remember in fourth novel he resisted against Imperio. So i think he was resisting against crucio also, wasnt he? i may be wrong.....

All of the above. Harry had started to develop an immunity to unforgivable courses. Voldemort used the elder wand(which Harry was the master of) to curse him so the pain didn't affect him. Also, 6 outta 7 horcruxes had been destroyed at that point, including Harry's, so Voldemort had to become weaker at that point, and Harry had become stronger, cause he no longer had a piece of Voldemort living inside him.