The morning rush-hour subway is unbearably crowded.
Tips
grammar
The pattern X 不堪 means 'X to an unbearable degree'. 不堪 = 'cannot bear/endure'. Productive: 疲惫不堪 'exhausted beyond bearing', 狼狈不堪 'in utter disarray', 破败不堪 'in ruinous condition'. Always use it for negative/uncomfortable states.
