-->
As in several other instances in the Qur'an, the "face", being the noblest and most expressive part of a human person, represents here man's "personality" in its entirety; and its being "tossed about in the fire" is symbolic of the annihilation of the sinner's will and his reduction to utter passivity.
The face is the expression of their Personality, their Self; and turning upside down is a sign of degradation and ignominy. When the Retribution comes, the evil ones will be humiliated, and they will wish that they had followed right guidance when they had the chance. They will then fall to accusing their leaders who misled them. But they forget their own personal responsibility.