Rooftop

Equip the Shotgun. Consider the Bulletproof Vest for damage reduction, but be aware it may hinder mobility, which is crucial.

Attack the Missionary from the side or behind. Frontal attacks are blocked by its blade hands and often result in you taking damage.

To get behind it, run past it as it attacks or use strafing to avoid its rushes. Land a Shotgun blast or kick while it's recovering or down.

When the Missionary moves away to reposition, run towards it at an angle to avoid its charges and get behind it.

Strafe to avoid incoming attacks when it rushes you, then immediately try to shoot it from behind or the side.

You can often get a shot in as it begins to run away, provided its back or side is exposed.

If you successfully block an attack or are out of its melee range, you'll often get another opportunity to shoot its exposed back.

If it turns to face you, run or strafe away to expose its back for another attack.

Repeat this process of avoiding attacks, repositioning, and attacking its exposed back until it is defeated.

The Missionary has several attacks: a thrust, standard swing, and running swing. It can also flail its arms when getting up and counter-attack if you are too close. Maintain distance and only attack when it's vulnerable.

If you run out of Shotgun ammo, the Handgun is a less effective alternative. Equip the Silencer to prevent the Missionary from blocking Handgun bullets. Melee weapons like the Katana are a last resort, used only for swings from behind after it misses.

After knocking down the Missionary about 4-5 times (requiring 6-10 Shotgun shells on Normal/Hard), it will stay down. Kick it to finish the fight.