Using an AutoFilter
is much more efficient than a range loop
Sub QuickCull()
Dim ws As Worksheet
Dim rng1 As Range
Set ws = Sheets("Sheet1")
Set rng1 = ws.Range(ws.[b2], ws.Cells(Rows.Count, "B").End(xlUp))
Application.ScreenUpdating = False
With ActiveSheet
.AutoFilterMode = False
rng1.AutoFilter Field:=1, Criteria1:="X"
rng1.Offset(1, 0).EntireRow.Delete
.AutoFilterMode = False
End With
Application.ScreenUpdating = True
End Sub