As always, PvP is a thing!
JC is omitted from PvP; either he wins for free due to a successful Tasha or loses outright. For epeen purposes, we'll assume he loses all his fights.
Alain enters level 6 with:
14 str, 14 con, 16 wis (needed for spells)
Combat Casting, Shielded Casting, Somatic Weaponry, War and Destruction domains
mwk bastard sword, mwk fullplate, +1 large steel shield
total HP 42.5, AC 21, +8 total attack bonus
mainhand avg 7.5
Batman enters level 6 with:
18 str, 14 dex, 16 con, 13 wis
Combat Reflexes, Improved Unarmed Strike, Ascetic Hunter, Two-Weapon Style.
mwk greatsword, +1 chain shirt
total HP 48.5, AC 22, +9/+8/+4/+3 total attack bonus
mainhand avg 13, offhand avg 6.5
Note: Batman's real weapon is a +1 guisarme, but he will be using a mwk greatsword for close range battle.
We will assume that Batman does not have a combat animal companion. We will also assume he chose Humanoid (Reptilian) and Outsider (Evil) as his two favored enemy choices. Humanoid (Human) is a reasonable choice for him but it makes the vs. Kaeli very one-sided. Outsider (Good) is not a reasonable choice for him, obviously.
Kaeli enters level 6 with: (4 bonus feats)
14 str, 18 dex, 14 con
Two-Weapon Fighting, Dodge, Mobility, Weapon Focus (scimitar), Combat Expertise, Weapon Specialization (Scimitar), Improved Two-Weapon Fighting (+1 feat that doesn't matter)
+1 scimitar x2, chain shirt
total HP 49.5, AC 19 (including dodge bonus), +8/+8/+3/+3 total attack bonus
mainhand avg 7.5, offhand avg 6.5
No one's feat choices are optimized for a level 6 fight. Alain is best taking Divine Quicken and Extra Turning and two-shotting people with basically guaranteed hitting inflict spells. Batman has a range of optimal choices but these get him closer to monk gestalt. Kaeli's options are focused on getting dervish early; her final feat is probably Spring Attack, Power Attack (as a prereq for Cleave) or One True Style, none of which do anything in these fights. Equipment is assumed to be appropriate for level 6 characters who are not spending consumables or have utility items; I think Kaeli's dual +1 scimitars might be overdoing it, I dunno. The gear level is probably low, but similar to what is likely to exist in the game; these characters are likely to rely on buffs to hit their enhancements rather than permanent +stat gear.
All fights begin in melee range. This disadvantages Batman (Alain has Shielded Casting) but I don't feel this is a big issue.
Alain vs. Batman
Alain's one attack has 30% hit chance, smite 50%. Spiritual Weapon is a little better, 35% for avg 6.5 damage. Bull's Strength brings him to 50% for 9.5 avg.
Batman's first two swings are 40%, second two 15%.
Alain has a very low chance of winning; Batman is outputting somewhere around 10 damage a round while Alain is stuck with around 6, and it takes him 2 spells to get there, meaning he's already behind 20hp. Even with heals, this seems unwinnable. Note that Alain's Cure Serious healing only heals 19.5 and costs him a round, for a net gain of 9.5 hp.
Alain vs. Kaeli
This fight is stupid. On paper, Alain wins due to heals; Kaeli can barely hit him and does low damage when she does, while Kaeli's AC is kind of low and Alain hits her 45%. However, that's not actually how this fight goes.
Kaeli can take -5 on Combat Expertise, bringing her AC to 24. This makes Alain's hit chance a mere 20%, while Kaeli has four 15% hit chances due to crits. Alain can go up to 30% with Bull's Strength, but Spiritual Weapon only hits 25%. Kaeli's doing a little over 3 damage a round, Alain is dealing about 5.5, Alain has to drop 2 rounds every 7 buffing (spiritual weapon first, then bull's, then attack until bull's runs out, then heal and repeat). With this pattern, Alain eventually outlasts her but it takes over a full minute of combat. He does have the spells to keep this up long enough (4 level 2s and 2 level 3s). Over 8 rounds, Kaeli deals 24 average damage. Alain heals 19.5 per Cure Serious casting, and he could keep up his full assault for 16, followed by bull's strength and another 5 rounds of 3 avg, followed by another heal. Even if the RNG favors her that far, he can expend one more heal, too (though with almost no damage output).
Batman vs. Kaeli
AC 22. Fucking hell that shit's imba.
Batman deals far, far too much damage to Kaeli; she goes down in 4-5 rounds on the average if she doesn't use full Combat Expertise. Unfortunately, that screws her down to ~3 damage per round, while Batman can still hit for about 7. Ugh. The RNG hella favors Batman here too, as a lucky crit could hit Kaeli for over half her HP (36 damage) while a max crit from Kaeli, even if she confirmed it (much less likely) would only do 22.
tl;dr: wtf e6 rangers
Super Alain Fighter 2 Turbo HD Remix
Hold Person is SL 2, giving Alain 4 shots (Spiritual Weapon is a domain spell so he got an extra one in the vs. Kaeli battle) to win. Alain has a save DC of 15. Neither opponent will defeat him before he gets all four shots off, and even in the event of unlucky RNG events, he can pop a heal. If his opponent is held, Alain gets to coup de grace (a respectful tap on the neck with his weapon).
Kaeli has a pitiful +2 to save, giving a 60% success chance. She is over 90% likely to fail by her third save. She has a 1% chance to save four times in a row.
Batman has +3, with similar chances. He will only win with favorable RNG.
Holding action to interrupt him is not ideal. A 30-40% chance to hit with a single attack is not ideal, and you can't hold a full attack.
tl;dr: battle cleric 2 stronk