How does Claudius treat Ophelia?
Claudius ignores Ophelia for much of her existence except when he needs to use her in a plan to discover the cause of Hamlet's supposed lunacy. Claudius and Polonius use her as a pawn to decide if Hamlet is is crazy because Ophelia has denied his amorous advances.
Claudius curtly asks, "But how hath she received his love?" (II,ii,137) and has only the mildest interest in Polonius' answer before agreeing to spy on their interactions. He later concludes that that Polonius is incorrect:
Love? His affections do not that way tend;
Nor what he spake, though it lacked form a little,
Was not like madness (III,i,176-178).