Besides the ending in The Chrysalids, where are other examples of irony?

I think there are plenty of examples of irony in this
text. Remember that irony is the gap between appearance and reality. It is incredibly
ironic that it is amongst the children of one of the most evangelical preachers against
abominations that a "super abomination" in the form of Petra is born. I am sure that
David's father must have been delighted when he found out (not). You might also like to
think about the fact that everyone was so earnestly searching for abominations of the
extra toe variety like Sophie that they were completely oblivious to a far more
insidious abomination that appeared "normal" right beneath their noses. Lastly you might
want to consider the fact that the force that is sent into the Fringes after David,
Petra and Rosalind actually contains one of the people that they are trying to hunt
down, who is therefore able to give valuable information to David and Rosalind and
co-ordinate their defence.

Those are the main forms of
irony. I think there is actually a deeper irony at work about the philosophy of the
Sealanders who come for Petra. It is highly ironic that the woman who comes to take
Petra seems to preach in the same evangelical and arrogant tone that David's father and
the Inspector preach in. Perhaps the new reality of life in Sealand isn't going to be
that great after all...