Thunderbolts by Warren Ellis

Warren Ellis's 2008 run on Thunderbolts for Marvel redefined the series as a brutal, black-ops team of reformed supervillains led by Norman Osborn. Over just two issues, this short but impactful arc established a darker, more ruthless tone that would define the team's modern era, showcasing Ellis's signature blend of gritty realism and sharp dialogue. Though brief, it remains a key turning point for the franchise, cementing the Thunderbolts as government-sanctioned killers rather than heroes.