So my character prefers things to live (in peace) but if they can't he needs to be able to defeat his opponent in a non-lethal manner.
He will kill to defend his or another's life, but otherwise would prefer to just subdue his opponent if possible.
He will kill monsters/beasts (things it's not possible to reason with) but will hesitate if it is sentient and can be dealt with non-lethally.
Even a wolf he'd rather frighten off (with fire) than kill it (but he would if it had a friend pinned).
In a previous thread it was stated that "the enemy will just come back to kill you so it's not worth letting them live." However, Batman is still a thing and my character has the same values.
I had thought of a magical item I called "binding vines" that could be used as a sort of "hand-cuff" for arms and feet or even to bind someone's arms to their torso. They would be small vines you could keep in a pouch and they would magically expand to bind the foe. They could be magically activated/deactivated or even given a time limit where they would release after a set period (like 2 hours to give the party time to get far away before letting go).
Does Pathfinder have anything like that? Would it be something that could be allowed in the game?
Also, I've been given tips like "blade of mercy" and "enforcer", are there any other ways as well that would be effective ways of defeating an enemy without killing them? And how about restraining them?
Nonlethal weapons are always a good option of course for subduing.
You could also use a heavy hitting weapon like a Great Sword and put Merciful on it, weapon enhancement that not only makes it do non - lethal (can be turned on / off with command word IIRC) but it does an extra 1D6 damage.
As for retraining an opponent being a good grapple character can help. There are rules to tie up up your opponents when you have them pinned, unconscious or otherwise restrained where the escape check is vs your grapple CMB (this is why having a decent grapple check helps) + 20. Also if the DC is higher than 20 + the targets CMB they can't escape, even on a natural 20 (they can just burst the ropes with a strength check still if you use rope, so make sure to have good quality rope if you plan to use it. Chains work too, they have a burst DC of 26 which is going to be hard for a lot of creatures to make)
It might be a tad extreme, but 4 levels in brawler gives you a reliable nonlethal attack, the ability to grab improved grapple when needed, and knockout 1/day.
On a more managable level, merciful weapons let you knock out creatures with nonlethal damage, a spell storing weapon loaded with stabilize will keep enemies from dying, and a high enough diplomacy will keep many fights from happening in the first place.
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Also, I've been given tips like "blade of mercy" and "enforcer", are there any other ways as well that would be effective ways of defeating an enemy without killing them? And how about restraining them?
Ways to deal non-lethal damage with lethal weapons without penalty.
Traits
Blade of Mercy (religion-Sarenrae): all slashing weapons
Merciful Scimitar (combat): scimitars
Mock Gladiator (social): any one weapon
Feats
Bludgeoner (combat): all bludgeoning weapons
Divine Fighting Technique (Combat-Sarenrae): scimitar
Merciful Bane (general): any weapon currently affected by your Bane class ability
Stage Combatant (combat): any weapon for which you have Weapon Focus
Virtuous Creed, Mercy (general): all weapons
Weapon Special Abilities
Merciful: any weapon
Tanglefoot bag
color spray
forcecage
sleep
web
beguiling gift combined with oil of taggit (Note that the onset time of the poison is 1 minute, so you'll have to find another way to deal with the enemy until the poison takes effect.)
Grappling and weapons with the grapple ability.
iron bands of binding
I might be pointing you in the wrong direction, but you could use handcuffs. They are from the Melee Tactics Toolbox and are called "Quickcatch Manacles." Of course, manacles aren't nearly as versatile as rope since they have to be sized to the victim.
Out of the Occult Adventures book, there is a Straightjacket. It causes the "Grappled" condition. An escape DC is listed, but not a break/burst DC.
I've also heard on the board from a group that carried around a suit of broken half-plate, a set of locked gauntlets (locked around broken weapons), and some rope or manacles for prisoners that they absolutely didn't want to escape.
kineticist with merciful foliage, turn all wood element blast to nonlethal at will with no cost or penalty
Just remember that non-lethal damage can still kill in Pathfinder.
If a creature's nonlethal damage is equal to his total maximum hit points (not his current hit points), all further nonlethal damage is treated as lethal damage. This does not apply to creatures with regeneration. Such creatures simply accrue additional nonlethal damage, increasing the amount of time they remain unconscious.