Infernus in Deadlock is generally read as having a rough, brash, possibly street-tough American-style accent , but there does not seem to be an official confirmed accent label from the game itself. Community discussion focuses more on his voice lines and personality than on a named regional accent.

Why people say that

His delivery comes across as cocky, fast, and gritty, which is why players often describe it as sounding like a casual urban or working-class American accent rather than something sharply defined. The available voice-line references show the character’s dialogue style, but not an explicit accent tag.

Best simple answer

If you want the shortest practical answer: he sounds like an American accent with a rough, rebellious edge. That’s the safest description based on the public voice-line material currently available.

TL;DR: Infernus doesn’t appear to have an officially named accent; he most often sounds like a gritty American-type voice with a rebellious tone.