Champion

The Champion is designed to be a Defender and Support class. In nearly all situations where want a Striker, a Barbarian will be a better choice.

The Paladin Paradox

You need to encourage enemies to attack other characters in order to use Retributive Strike. Using "Raise a Shield" increases your AC, encouraging enemies to attack your allies instead of you. If you don't stand next to your allies, enemies can just walk away from you in order to attack your allies without the threat of Retributive Strike.

Class Feats

Level 1

• Everstand Stance (1/5) - Attacking with your shield is already rather situation and there isn't much support for your free hand as a Champion. You can't increase your weapon damage die size more than once, so you can't get it to stack with Deific Weapon.

Archetypes and Dedications

Sorcerer/Oracle/Cleric/Witch - Get access to the Divine Spell List, very useful if your party wants to cast divine spells.

Barbarian - I like this more than Fighter even though Fighter is more flexible. I consider Sudden Charge essential and Rage doesn't hurt the Champion too much (you lose the ability to Demoralize but you can Demoralize then Rage on a failure). The Giant and Spirit Insticts are great but the Superstitious Instinct won't work with the Champion.

Fighter (Boo) - Not much of a fan here since Champion should largely be avoiding Dexterity. The upside is more flexibility in Class Feats and the option to get Attack of Opportunity early (and outside of the Champion's Class Feats) but you don't benefit from the Dedication itself or have a chance to get Fighter Resiliency.

Marshal Dedication - Buffs the party and most Champions are at least somewhat reliant on Charisma (CHA) and it's potentially a useful way to pick up Attack of Opportunity outside of your Class Feats (at level 8 instead of level 6). Dread Marshal Stance and Inspiring Marshal Stance are good but potentially conflict with Rallying Charge (equivalent to Sudden Charge). Free skill progression is always nice as well.

Tips and Tricks

Don't forget about Shield Bash (and Shield Boss or Shield Spikes). As long as you're holding a Shield, you have access to a specific attack that deals 1d4 bludgeoning damage. Investing in a Shield Spike increases that damage to 1d6 and provides piercing damage; if you prefer bludgeoning damage but want the larger damage dice, get a Shield Boss. This allows your shield to compliment your primary weapon's damage type and makes it possible to cover all three physical damage types with a Versatile weapon.

FAQ

Can Champions cast Divine spells from scrolls?

No, Champions do not have access to the Divine Spell List without picking up a Dedication.

https://www.reddit.com/r/Pathfinder2e/comments/com0j5/can_a_champion_activate_a_divine_scroll/ https://rpg.stackexchange.com/questions/202142/can-champions-cast-divine-spells-from-scrolls https://rpg.stackexchange.com/questions/158109/is-there-a-way-for-a-champion-to-gain-access-to-cleric-spells

Deific Weapon Cheese (might also be useful for Magus or Cleric)...

https://2e.aonprd.com/Weapons.aspx?ID=12

While not a huge edge for the Champion, choosing deities who have a Staff as a Favored Weapon provides a small bonus. A Staff is a d4 weapon with the Two-Handed d8 property. Deific Weapon increases those values to d6 and d10 respectively.

https://www.reddit.com/r/Pathfinder2e/comments/dqg4cl/deific_weapon_and_staves_is_two_handed_damage/ https://www.reddit.com/r/Pathfinder2e/comments/imxtyw/any_reason_to_use_simple_weapons/

Do Thrown Weapons work with Retributive Strike?

Yes, if you have Ranged Reprisal. Throwing a weapon is a ranged attack using a ranged weapon, so all of the benefits of Ranged Reprisal apply to the weapon being thrown.

Can a Paladin be trained in Deception or Thievery? Are they allowed to lie?

Yes, as long as you are following the more important tenet.

From the Champion's Code:

Tenets are listed in order of importance, starting with the most important. If a situation places two tenets in conflict, you aren’t in a no-win situation; instead, follow the more important tenet. For instance, as a paladin, if an evil king asked you if you’re hiding refugees so he could execute them, you could lie to him, since the tenet against lying is less important than preventing harm to innocents.

In the case of the Deception Skill, Feint is a common combat maneuver to break an opponent's guard; there's no reason a Paladin wouldn't use this skill (faking an attack is much different than throwing sand in their opponent's eyes).

In the case of the Thievery Skill, Disable a Device can be crucial to your party's success and there's nothing wrong with using that action.

https://www.reddit.com/r/Pathfinder2e/comments/rocitv/if_youre_a_paladin_are_you_never_allowed_to_use/

Can I use Blade Ally to give a Magical Staff a Shifting rune?

No. Specific rules trump general rules. Blade Ally asks for a weapon or Handwraps of Mighty Blows (a specific worn item), Magical Staves are not weapons even though they act like weapons.

An adjacent example to this is that you can't use Blade Ally on a Shield because of how Shield Bash works:

A shield bash is not actually a weapon, but a maneuver in which you thrust or swing your shield to hit your foe with an impromptu attack.

https://paizo.com/threads/rzs43rh4?Spellstrike-Staff-with-Shifting-Rune