ISB ~ 2 Thessalonians 1 v8

inflicting vengeance:Assurance that Christ will right every wrong and repay the wicked for their malice should encourage believers to refrain from avenging themselves by personal retaliation (Rom 12:19; 1 Thess 5:15).

do not know God:Unenlightened pagans (1 Thess 4:5).

do not obey the gospel:Such as the unbelievers of Israel (Rom 10:16).