According to at least one source, "abject" can be a verb, so there are no outright mistakes here.
However, since 'abject' is not a common word, you may want to add some more information to the sentence, like:
"After all his rebellions, he swallowed his pride and abjected."
"After all his rebellions, he abjected to the pressure of his superiors."
"After all his rebellions, he abjected, casting aside past transgressions."