This can undermine the teleological argument, depending on how its formulated.
For instance, the argument from complexity infers a god based on, well, complexity of things in the natural world.
I cannot understand what do you mean by "a god based on complexity of things in the natural world".
If complex evil things don't need God as a creator, why would complex goid things need God as a creator?
Who say complex evil things don't need God as a creator?
You mean the statement "evil is not the nature of God" must necessarily have the same meaning with the statement "complex evil things don't need God as a creator"?
... and by doing so, they assume that things that are not in line with the "nature of God" don't require God as their ultimatr source. If some things don't need God, why does anything need God?
Assumes God is omnipotent.
Assumes the nature of God is good but not evil.
Assumes God creates everything including evil.
Assumes God says that among those everything, the things which are good should be understand by his follower to be his nature. The things which are evil is not his nature.
Assume it is not necessarily that God's creation must be inline with his nature.
According to the assumption above, it is possible for God to create things which are not inline with his nature.
Therefor the things that are not in line with the "nature of God" do require God as their creator.
According to the assumption, God is omnipotent, this imply he can create things which contain new element which does not found inside himself or his nature, the new element is evil.
So it's possible that the evil doesn't require God's nature as the ultimate source to form their existence.
In another possible explanation, maybe originally God's nature indeed does including evil, as time goes by God manage to overcome it and so God's new nature doesn't include evil anymore.
Just to clarify, i don't have the belief that any assumption mention above is true nor i having the belief that they're false.
I'm discusing about them hypothetically.
You said "If some things don't need God, why does anything need God".
I'm sorry, to put your statement in the context of the assumptions above, i have to modify it, but please be understand i do not imply that my modify version is the only possible interpretation nor that there's no alternative interpretation for your original statement in other explanation.
My modify version will be:
If it's not necessarily for God to use his nature as the source or forming element to create things, why does any other things which form by using God's nature as source, need God to create their existence? Why couldn't they just exist without God create them?
Shorter version will be:
If some things don't need the nature of God as a source to form their existence by God, why does any other things need God to create them so that they can exist? Why couldn't they just exist?
It's non-sequitur.
According to the assumptions above, God can use his nature as a source to create things.
God can also invent new element which is not his nature, as a source to create things.
The reason that some things don't need the nature of God as a source to form their existence by God, doesn't explain why any other things have the abilities to just exist without God create them.
I think you're missing a major link in the chain: the part where you connect the existence of a thing (or a set of things, or all things) to God. Once you have that justification, we'd have to ask whether it would apply to things that aren't in line with "God's nature".
According to the assumptions above, it's possible that the evil don't require God's nature as the ultimate source to form their existence.