‘T.K. Sabapathy is one of the most respected and regarded art historians in Southeast Asia,’ says a poster advertising a talk. Note that respected and regarded share a modifier, most.
Most respected is all right: I can respect a person a little, a lot, the least, or the most.
Regarded, however, needs more than just that: we can’t say a person is regarded a lot or a little; rather, we have to say she/he is highly regarded, etc.