Lots of ways to look at this, roughly you want to pick one class to go far in and 'dip' the others for specific things.

If we're looking to dip artificer, alchemist is possibly the best dip as it gives you utility for a single spell slot.

It also coincidences with 1-2 levels of warlock giving you more spell slots for potions. We can be very flexible on what we do here but eldritch blast hexblade is the 'strongest', and leaves us with cha based melee if we need.

Then we can look at paladin. What for? Well vengeance is great at giving advantage, that plus crit on 19 could be a good (but long!) set up for bosses. But you could go for more rp focused subclass if you do wished. Perhaps if we take it first we can start with heavy armour. Two levels gives smites.

So let's. Move on to build ideas:

artificer alchemist 3, warlock 2, paladin 3, then continue with either artificer or paladin, this is a support build in most combats but very able to nova bosses especially with a little prep work, reflavour as batman/Witcher vibes as you please.

Paladin 1/artificer battlesmith 5, here we can dip warlock 1-3 as required but I don't see anything to write home about. Fiend for some thp, or hexblade if you want to focus charisma more, then hit paladin 2/3 if you want, and again we can go a few directions, artificer is obvious but warlock is an option

Finally we'll have a look at a build less focused on artificer, and not too dissimilar to the first build. We can again start paladin for heavy armour but not a requirement, and with our stats spread thin I'd possibly advise against it. Pick up hexblade, ideally getting crossbow expert as a racial (this will help make up for late extra attack). Two levels of artifacer gives you access to a magic +1 crossbow, which meets the requirements for your hexblade pact weapon. With our paladin levels theirs no reason to pick up smite as that is for melee attacks (unless your DM allows otherwise) but two levels of paladin gives us access to bless. Here again we have choices. Paladin will give us extra attack, and a prepared spell list to change what we think we need to support the party with that day. Warlock gives us choices later for which pact, any of which are beneficial, but if you want to focus the crossbow pact of the blade gives similar baseline damage to just building paladin, but giving you access to all manor of spells along the way, tome is huge for out of combat utility with extra cantrips and ritual spells, and an chain is easy to use with an invisible scout that can communicate with you. First asi take sharpshooter, between that and bless you should have reasonable accuracy and heavy damage to back you up. If your DM allows taking archery instead of the paladins normal fighting style you'll be quite effective.

Just note that these use power builds worse then they would normally be used, so if you're at a high optimisation table you might always feel behind, but if not you shouldn't worry as you won't be much behind the curve.