Calculated column if a task repeats

You can try something like this:

Rept = 
VAR varKey = table[Key]  

VAR varSprint = table[Sprint]

VAR varSprintMin = 

    CALCULATE ( MIN ( table[Sprint] ), table[Key] = varKey )

RETURN

IF ( varSprint = varSprintMin, BLANK (), 1 )

varKey saves current key as variable

varSprint saves current sprint as variable

varSprintMin calculates minimum of sprints for all rows with same key as current key

return value: if current sprint is minimum of sprints with same key, returns BLANK, else 1

-- editted for formating reasons