Do not use comparatives (more, less, longer, clearer) unless you mean to compare two things and you specify what those two things are.
• Wrong: King Lear is longer.
• Right: King Lear is longer than Macbeth.
Likewise, do not use superlatives (most, least, longest, clearest) unless you specify a comparison group.
• Wrong: King Lear is the darkest tragedy.
• Right: Of Shakespeare’s tragedies, King Lear is the darkest.