How can a dictator be removed when the he/she doesn't have any challenger?
Take, for example, Bangladesh's sitting PM Sheikh Hasina.
She has strong political backing from India as they played an active role in removing the army-backed government and putting her in power in 2008 (1, 2). After coming to power, she took control of the army by a massacre (3, 4), executed some of her political and ideological opponents using a kangaroo court (5, 6, 7, 8, 9), threw her main political opponent into prison (10), took control of the judiciary (11, 12), over the years hundreds of people were forcefully disappeared (13), two sham general elections were held in 2014 (14) and 2019 (15).
As a result, she has no opponent left who can challenge her. She is practically immune to removal.
I think the West is not speaking against her sham elections and all other autocratic maneuvers only because India is with her, as the West doesn't want to lose the Indian market.
Now, the question is, in this situation, what opening can the general population look for to remove this authoritarian PM?