If it's causing you major grief, use a Radiance with detonate antimatter.  That will shut down power surge (at least until disruptive strikes shuts you down, so ensure you have the firepower to make it stick).  The one risk is that the Radiance is absolutely the wrong choice of capital ship if your opponent is leading Vulkoras or Skirantra, so unless you're psychic this will have to be your second capital ship.

That is not a large fleet at all; that's actually a very small fleet, and I wouldn't engage a high combat-value capital ship like the Kortul with such a small force.  High combat value capital ships are risky to engage with small fleets like this, and the Kortul is perhaps the most deadly of all.

Your only real option is to lead with Halcyon against Vasari.  Focus on his frigates and try to isolate the Kortul.  You can take it down if your fleet is large enough and it doesn't have support, but don't even try if it's got backup.  I only attack capital ships when I know I can make it count.




He probably had a repair platform here.  A single overseer would also make your attempts to take down the Kortul futile.

Now, against massed flak, you want to be very careful with strike craft.  You should probably be phasing in some disciples or destras.  Vasari sentinels are particularly nasty and you need to hit them with the right units.  You should probably try to stay one step ahead of the enemy; just presume he's going to counter your carriers so your own counter-measures come on the field in time to beat his.

Micro is particularly critical with strike craft.


The big problem is that the Advent illuminator just isn't very effective against capital ships.  Vasari and TEC can mass up a chunk of LRF to beat back the Kortul with sheer firepower, but since the illuminator bug fix the illum really can't manage that well.  This leaves you with very few options, and this is affecting Advent's ability to counter more than just the Kortul.



I love the Kortul opener, it's a great strategy, but the bottom line is that it's still a second tier strategy compared to the carrier opener.  Still very good if you know what your doing, but not a top-pick strategy.  I personally love it, the player you fought clearly did as well, but it's really more along-side the Vulkoras rush as something that's most powerful if your opponent doesn't see it coming or doesn't know how to counter it.

Basically prior to the release of Diplomacy there was a bug that effectively doubled the illuminator's damage.  It could beat the other LRF without even using its sidebeams, and when it did use its sidebeams it tore them to shreds.  Absolutely a monstrous unit; multiplayer was basically all about sending your money to the nearest Advent ally so he could build more illuminators. 

Back in 1.181, the patch prior to what you played, Advent was god.  Their illuminators were scary powerful, but this was just the tip of the iceberg of the Advent powerhouse.  They would rush you with disciples and seekers.  The seekers could easily kill any LRF in your fleet, removing assailants and javelis, giving the Advent disciples free pickings.  Leading that fleet would be two halcyons.  Even if this didn't work, the Advent would bring out the illuminator en-masse and your fleet (which was being pressured by light frigates) would be low on strike craft and flaks to absorb the punishment. 

It was extremely difficult to even survive, let alone beat, a competent Advent player back then.  Vasari in particular had trouble surviving, and as a rule if they started in rush proximity to Advent they would lose if they didn't get a starbase operational on either their own or their enemy's homeworld.  Despite this, many of the top players migrated to the underdog faction and developed powerful Vasari strategies to rival the incredibly overpowered Advent.

Patch 1.19 nerfed both the seeker and the illuminator, essentially killing Advent's standard opener.  Their strength had been entirely based on the overpowered illuminator and the powerful seeker capable of keeping the strongest enemy units off the field.  With those chips removed from play, Advent just couldn't handle a rush, and Vasari strategy is much more than it was in the early days of 1.181.  The result is an Advent faction that just can't compete, and a positively scary Vasari game plan.

Don't attack kortul if you don't have firepower to kill it. And whatever you do try not to feed it experience. LVL5 kortul can recharge a lot of shields.... But 2 Carrier caps with 3-4 drones all bombers on should be able to do it. once it runs out of AM it will die..... soon  

If you look at late game advent is only race than can compete with vasari fleet.

The problem they have is that they need a lot of research to be able to compete with either race at start. They are underdogs at start unless you are rushing with strategy mentioned above. It still works. Especially against vasari. It needs a lot of micro but....

You can pull off Advent in 1.19, but it's very difficult.  You'd probably have much better luck as TEC or Vasari.

 

Chase after them and counter-attack.  His lone Kortul might bombard some planets (you can use emergency facilities to slow him down), but you can rip up his far more expensive infrastructure and cripple his attempts to build up.  He'll lose this tradeoff, and all the while your fleet is growing while his is getting whittled away.

You can also stop him from taking asteroids with a pack of turrets. 

 

As I said, if the Kortul is proving too much to handle, the Radiance is your solution.  It will completely stop his power surge and let you finish him off.

You're right that it's not a foolproof strategy, but the fact is that if you're fighting with a fleet plus capital ship while he's just got a fleet in the early game, you can deal some heavy damage to him.  The big goal is to just buy time until you can smash the Kortul.  It doesn't take that long to build up to fleet sizes of 30 or 40 frigates, you've just got to keep him occupied while you do so and minimize losses.

 

It will slow down the rate at which the first capital ship will gain experience, meaning a weaker Kortul and less powerful power surge individually.  Still pretty nice, but not twice as dangerous.