Use 'botch' when someone does a task incorrectly due to errors in action, not just bad thinking. He botched the painting by using the wrong brushes.
Pro Tip 2/3
Avoid Exaggeration
'Botch' often implies a serious error, not a small or trivial mishap. We can't turn in our project like this; we've completely botched the calculations!
Pro Tip 3/3
Casual Tone
Often found in informal speech; not typical for formal writing. Oh no, I’ve botched up the whole recipe now!