How does Winston show that he is not entirely true to big brother?

Winston demonstrates his lack of loyalty to Big Brother through his secret rebellious thoughts and actions, such as writing in his diary, which is an act of defiance against the Party's strict control of individual expression. He engages in a forbidden love affair with Julia, further highlighting his desire for personal freedom and emotional connection, which stands in stark contrast to the Party's ideology. Additionally, Winston's growing skepticism about the Party's Propaganda reveals his internal conflict and disillusionment with Big Brother's oppressive regime.