BAYONETTA

Simply buy all techniques in the shop. This will come naturally enough but here are some tips for earning halos without grinding.
More points = more halos.
Use the Gaze of Despair accessory. Enraged opponents are worth more points!
Keep your combo going. If you're too far away from an enemy, use X to shoot them. This does minimal damage but will stop your combo from timing out.
Use torture attacks to quickly boost your combo multiplier and cause enemies to drop their weapons.
Use angel arms. These give absolutely ridiculous points per hit. The B attacks with the polearm, bow and arrow and flame claws are especially OP.
Fight in witch time as much as possible. This also boosts your points.
You can also use long taunts (hold down the taunt button) to freeze the combo timeout counter. Useful if the next wave of enemies hasn't spawned in yet.
Finally, know that the combo multiplier doesn't stop at 9.9. This is the highest number the game will display, but internally it keeps getting higher and higher.

If you can make use of all of these tips, you can earn enough halos for this achievement from chapter 2, verse 3 alone.