The mutation with the greatest consequence are insertions and deletions. These mutations is more damaging because it will lead to frameshift mutation. A frameshift mutation is present when there is an addition or deletions of nucleotides. The resulting shift leads to the changes in the coding of amino acids. This will eventually result to a protein that is nonfunctional. The protein that are produced have a complete different chemical compositions. The outcome of this shift is a complete alteration of the sequence of amino acid.
A substitution mutation will only alter a single amino acid.