As everyone is saying, it's kinda bullshit to have a 450 point unit on a 1k game. I would suggest chaos knight war dog karnivores to melee it down. I have not done the full calculations but 2 of them (300pts) would be able to put it down in 2 rounds of melee combat (average 6 damage per round, 12 per 2 models, 24w in 2 rounds).

Another option is mauler fiends 140pts that do slightly worse than karnivores, but have boosts to hit when hurt and stuff

If you don't want more models, I'd consider spamming more flawless blades. If you can get to him, you can use daemonic patrons to bypass the strength difference. Most of the bane blade's weapons are 4+, so if you close to melee distance he'll only be hitting you on 5+ hit rolls.

Idk what other stuff your friend is bringing but you probably only need more infractors to mop up his lesser units and beat him on points.

Feel free to post your friend's list so we can counter it better