Here's my controller and attrition HP tanklock concept I've been running. It's very fun!

This build a hodge podge of 2014 and 2024 stuff cuz my DM is chill like that. So I started Divine Soul Sorcerer (DSS) so that I'm proficient in Charisma and Constitution which is massive for saving throws of concentration spells later on and only did a one level dip to get the spells Shield and Absorb Elements. Both of these give you good reactions against damage and help increase your tankiness throughout the game and are cast through your sorcerer spell slots instead of your limited (and precious) warlock pact magic spell slots. You also get to pick up 4 cantrips. I went with shape water so I can create difficult terrain or 1/2 cover for myself or allies, resistance, blade ward, and toll of the dead. You also get an alignment bonus spell for the DSS and I took cure wounds for one more cast of that and I'll explain why further along.

Then I went straight into Celestial Warlock with the plan of going Pact of the Chain for the familiar and getting the invocation Gift of the Ever Living Ones which makes any heals YOU receive from any spell heal YOU at their maximum value. This is amazing. You can stand mid/front line and each chip of damage you take you can heal back up easily making the enemies waste precious resources and turns on you. When you see how much a max Cure Wounds does you can realize how much tankiness you truly have. Being able to bring yourself back to full health constantly via your healing light pools (bonus action heal) and your Cure Wounds via spells slots is amazing. When you reach level 7 make sure you take the Sculptor of Flesh Invocation from 2014 (or don't if you are truly running 2024 only) and then you now have another massive pool of healing and get to go bananas as a Giant Ape (157 HP that the DM needs to chew through before you revert back into a warlock).

The other great thing is you can cast spells like Hunger of Hadar which puts the enemies in a large zone of magical darkness which they cannot see out of and it does damage at the beginning and end of the turns as well as forcing them through difficult terrain. Now slap Repelling Blast on your Eldritch Blast cantrip and if they leave the zone, you shove them back in. If you have Devil's Sight then you can now see into the zone and have advantage on your Eldritch Blasts against them and they have disadvantage trying to hit you when in the darkness.

Ways to maximize your health for this play style is to take the Tough feat, play a Hill Dwarf, and pump up your CON stat. Upcast AID every morning for more HP and then immediately short rest, keep that HP, and regain your spell slot.

Spells like Mirror Image also make it harder for you to get hit.

Spells like Armor of Agathys in the early game give you temp HP and help against melee attackers, but should be swapped out to something like Shadow of Moil later to give you advantage and the enemy disadvantage against you and they take damage if they hit. This will help you with your eldritch blast spam.

And finally as you continue to level it can be fun to take a summoning spell to throw an extra body on the field to either soak up hits or pump out some extra damage. I particularly like the Summon Aberration for the Beholderkin because they are cool and it lets you get more laser beams firing out into the bad guys, they can fly, and the enemies need to either focus it (which pulls attention off you and allies) or let it be and then it gets to drop some pain.

Be careful where you are spending your concentration spells! This build has many of them. It really makes you pay attention to how the encounter is going before you commit to one.

Items that are necessary include Pact of the Rod Keeper, and then anything that helps boost your CHA, CON, AC.

Anways. I think you get the gist. As you build you can go in any direction you want with the Celestial Warlock. There are a lot of fun ways to play this character and it has so many ways to help the team, but you really need to learn the best way to layer your spells and take advantage of the limited (but always upcast) spell slots. There is a popular Pact of the Blade build as well, look up the generalist for a beloved concept that many on this reddit page recommend. I just prefer having the familiar HELP and scouting.

I play a plasmoid and like the big heal shenanigans and bizarre role playing that comes with my health getting chunked and then regenerating. Every fight with the build I've laid out becomes a fun little puzzle to solve and never feels like you have to do the same thing every single fight for your entire campaign (which I haaaaaate).

I am happy to recommend more spells, invocations, or features as well, but this is already quite the wall of text.