Hel-Raiders are essentially just recoloured Raiders, although they're perhaps a touch more aggressive (maybe because they're dead, we can't say for sure). Anyway, the same tactics apply.
Raiders will almost always come at your swinging, but that makes them easy to predict. They're standard humanoid enemies, so a couple of good parries should be enough to stun them completely, and leave them open for a finisher.
While their aggression does make them easy to read, as mentioned, you still have to be careful when fighting multiple Raiders at once. They'll come running at you from any and every angle, so try not to get surrounded.
How many Hel-Raiders have you smashed into submission? Be sure to check out our full God of War Ragnarok guide for information on how to beat every enemy, and much more.