WordNet sense 1 (marked by excessive confidence):

cocksure, positive

WordNet sense 2 (marked by assurance; exhibiting confidence):

assured

WordNet sense 3 (persuaded of; very sure):

convinced

WordNet sense 4 (having or feeling no doubt or uncertainty; confident and assured):

certain, sure

WordNet sense 5 (not liable to error in judgment or action):

surefooted, sure-footed

WordNet sense 6 ((usually followed by `of') having capacity or ability):

capable