Complex sentence: During the final onslaught, all the revolutionaries are killed, except for Marius, who is wounded severely, and Valjean, who escapes with the unconscious Marius through the sewers.
Split into simpler sentences: During the final onslaught, all the revolutionaries are killed, except for Marius, who is severely wounded. Valjean escapes with the unconscious Marius through the sewers.