Kieran Culkin’s mile-a-minute turn in A Real Pain was the single most lauded performance of this past awards season, winning pretty much every best supporting actor prize on offer, up to and including his Oscar two weeks ago. As an erratic, unfiltered loose cannon joining his strait-laced cousin, played by writer-director Jesse Eisenberg, on a Jewish heritage tour of Poland in honour of their familial roots, Culkin is rivetingly reckless and off-kilter in the part. The awards are well deserved except for the key detail that it isn’t remotely a supporting role. An evenly weighted two-hander (now streaming, and on...