be the last person

be the last (person) to (do something)

To be very unlikely or unwilling to do something. You know I'd be the last to question your judgment, but perhaps you should get some outside help for this. I thought she'd be the last person to go for such a strange plan, so I was shocked when she agreed so quickly.
See also: last

be the last person (to do something)

to be the most unlikely person of whom one could think in a particular situation; to be the most unlikely person to do something. (Also literal.) Mary is the last person you should ask to chair the meeting—she's so shy.
See also: last, person