What types of mutation that affect segments of chromosomes are least likely to be important in evolution

Explain please.

My answer would be Deletion.
Deletions result when a gene is mistakenly removed from a chromosome, again often as a result of unequal crossing over. Often zygotes produced by gametes involving deletions are not viable since they do not have the full compliment of genes... Since there is no offspring to continue the generation, there can't be any evolutionary aspect of this directly and is least important in evolution.