Soyuz 2.1b
The 2.1b version adds an upgraded engine (RD-0124) which greatly increases the specific impulse of the upper stage (326 seconds to 359 seconds), and hence improves payload capability from 7 tonnes to 8.2 tonnes.
Missions: 90
Successes: 87
Partial Failures: 1
Failures: 2
Success Streak: 54
Success Rate: 97.2%