Pretty broad kind of request… so its hard to answer in any detail…
Obviously I am gonna assume you looked through the builds on lastepochtools - those are usually the most powerful end game Paladin builds…
Trying to stick with Paladin builds…
All the Smiter builds - i.e. Javelin, Shield Throw & Hammer Throw that proc Smite are generally powerful and good to use end game and are probably the most popular too… Easy to play, you just have to understand that you are proc’ing a spell skill so you have to spec your gear and build to gain the most benefit for this type of damage vs throwing damage…
Warpath is probably the next most popular and is a playstyle that a lot of people really like… It can be very effective and because you are moving constantly, there are lots of very powerful and tanky interactions that make it a pretty decent route… The void knight warpath is probably stronger, but a paladin warpath is still viable…
There is also a Multistrike build that (wait for it) can proc Smites which makes it look like you are raining hellfire over the map while you beat the stuffing out of mobs… Similar Javelin Electrify DoT build which I am messing with right now that is actually surprisingly fun to play once you figure out mana management…
Vengeance is a very tanky skill but is out of favour right now - used to be, everyone had a sentinel build with Rive & Vengeance but its sort of an afterthough at the moment - still possible to build around it but when people see content creators using other skills old vengeance is generally forgotten… Judgement is fairly lacklustre unfortunately (imho at least) but some people do have builds that use it…
The key thing imho is that Sentinel builds have a lot of opportunity to proc secondary things which tends to make builds much better than just a traditional tank with a sword & shield… and there are some clever interactions - both from gear and skills - and yes, you can use some forge guard & void knight passives/skills even though you are a Paladin, that make builds pretty op and allow for a wide variety of possibilities
Without giving away spoilers, there are various unique items that can take all of these builds to the next level depending on how you build them. Everything from a sword and spear that boost smites and multistrikes to amulets that boost smite damage based on how much mana you dont have to chest armour that gives you a flat 40% damage reduction while moving which is obviously wonderful for warpath… and thats just a few that come to mind…
Most tanky… well, if you watch some of the build videos floating around you will see that there are Rogues that can be virtually immortal… mages/acolytes with a crap ton of ward, druids & primalist bear builds that seem like nothing can kill them… and yes, sentinels with 90% armor and 100%+ block and so much damage reduction that they can tank everything except the boss one-shot mechanics (yes there are some of these, but thats a different discussion)…
Two button win… This is something that you will struggle to find a lot of although there are (especially if you use the auto-cast numlock trick)… There are definitely a few builds that do fall into this category tho… warpath builds for example are often a very simple playstyle. The devs have expressly said - on numerous occassions - that they want people to interact with the game and dont want skills to be ignored or not used as part of a rotation - in fact, they have said that if that occurs, they would rather redesign the skill to make it more worthwhile to actually use…
That should give you a high level kinda answer… dont really want to get into the specifics as I feel like that would take away from your discovering these things yourself while playing…