simple question (i hope)

Okay, so I have a spell that summons 2 units when it casts, and I want to make a trigger that deletes one of them. I've tried something like

event: a unit casts a spell

condition: ability being casted is equal to <ability>

action: remove (last created unit) from the game

but that doesn't seem to work.

Just alter the spell so it only summons one. Im thinking your talking about feral spirit and it can be changed in the Ability Editor to only summon 1 instead of two.

why do you want to delete one? Why not just set the spell to only summon one?
I think created unit doesn't work when refering to summoned units (might be wrong though)

Because of the editor bug at high levels. Its a spell based off serpant ward, that summons better wards each level, all the way up to level 7. But levels 5-7 won't work unless I change the default number of of summoned units (1) to 2 or more, so I thought the easiest way to fix it would be to just have all of the levels summon 2 wards, and have a trigger that deleted one of them each time.

I think there's an event response called Last Summoned Unit.

If there is, I don't see it... theres a "summoned unit" (which doesn't work either), but theres no "last created summoned unit" that I can see.

I don't think you can do that. Its because summoned units are created simultaneusly. So even if your trigger worked, it would either destroy them both or destroy neither.

god i hate this editor and all of its bugs

You could make the spell do nothing, but then make it summon the unit using a trigger.

Yes, that would be easiest. Except, their is no way for a trigger to check the casted spells's level. If you are only using 1 unit EVER that has the spell, you could make a seperate trigger that finds out when the spell is leveled up and adds 1 to an interger variable, then use if/then/else actions on your summoning trigger for each level.

You could do it with a couple people casting it too. It would take variables and maybe arrays but it would work.

Reffering to last created unit only selects the last unit made with the trigger 'creat unit' If you wish to create only 1 unit from a spell, you either have to tell the spell to create only 1 unit, or do something like this:
Event: Units finishes casting an ability
Condition: Ability being cast == "ability"
Action:
Pick every unit of type "creature" owned by "player {
if(number of units of type "creature" is greater than 1) {
removed picked unit
}
}
This will only work if the ability allows you to only have 1 creature of that type, period.