In T20Is, there have been only three completed innings when the extras have been the highest scorer. Out of these three completed T20Is innings, only one has come in World T20. Ireland holds this dubious record in World T20.
The incident happened in 2010 World T20 when Ireland was bowled out for 68 while chasing 138 for victory against West Indies at Guyana. There were 19 extras in this innings with GC Wilson being the second highest scorer with 17 runs.
The other two instances in T20Is have been in the West Indies innings against South Africa at Johannesburg in 2008. West Indies had 29 extras in the innings with the second highest scorer being DJ Bravo who scored 24.
The third instance happened in the Canada innings against Scotland at Dubai in 2012. There were 23 extras in Canada innings with HS Baidwan being the second highest scorer with 21 runs.