To answer the question posed in the title - you'll know them by their flaws.
In case you aren't familiar with my theory of the malformed werewolves on Teen Wolf.
...because Alpha werewolf sparks can only make new werewolves. That's what it does.
It's pretty much its only unique function. It makes new werewolves.
But my comment section says in unison "an
alpha spark made Jackson into a kanima and Kate into a cat lady".
No, the alpha spark did no such thing. It tried to turn them into werewolves.
The alpha spark shot out a little werewolf spark
through bite and scratch in an attempt to make a new werewolf.
But their twisted souls overwhelmed the little spark and made them into those other things.
But with a normal soul, the spark always makes a werewolf because that's all it can make.
We know Jackson as a kanima was a malformed werewolf because Derek basically said he was.
Derek: It's called the kanima. Scott: But it's like us?
Derek: A shapeshifter, yes. But it's it's not right.
Allison: The kanima was actually supposed to be a werewolf but it can't be.
Scott: Until it resolves that in its past which manifested it.
In addition to a loss of individuality and control,
the kanima shape comes with a ticking clock.
Derek: Meaning what? It can
turn to something bigger? Peter: Bigger and badder.
Derek: He's turning into that? That has wings.
If he doesn't resolve his issues, the individual will be lost forever inside a beast.
Derek: Gerard controls him now and he set all of this in
motion so that Jackson could get even bigger and more powerful.
Chris: No he wouldn't do that. If Jackson's a dog, he's turning rabid.
And my father wouldn't let a rabid dog live.
Gerard: Of course not. Anything that dangerous, that out of control is better off dead.
These are the flaws that come with that specific malformation and if we
use Jackson as the template we can compare the other supernaturals to see if similar
flaws define them and suggest they're just another malformation of the werewolf spark.
Kate is a tricky one to start with because her flaw isn't
as obvious as Jackson's or some of the others.
The only thing we see that's a clue to her malformation is that
she still had no control of her transformation after many months.
We saw people like Scott get control after only a couple of full moons. The same was true of Isaac
and Boyd. I'm not including Erica here because we never actually saw her in control on a full moon.
Attendant: Hey, you alright?
Hey! Kate: I'll be out in a minute!
Attendant: You okay?
For Kate, almost a full year into her transformation,
for her not to be able to maintain some control on the full moon seems like a
sign that something is seriously wrong with that werejaguar shape.
It was so bad for her that she had to come up with a whole harebrained idea to de-age Derek's mind in
order to get hold of a trinket that offered the promise of some semblance of control.
Recorded voice: these born wolves had to be trained. They needed to learn control.
They had a practice for the training of betas
It involved the use of a sacred object called a triskelion.
So let's chalk the werejaguar flaw up as debilitating lack
of mental control over the internal monster.
Looking at Malia, the werecoyote, I think the flaw is obvious.
That theft of a fully formed spark at birth comes
with all sorts of problems for both the mother and the child.
For the Mom it's obvious, she loses a number of points off her power scale.
Corrine: What you do have is power, strength, speed
and the capacity to heal and do you know where you got it from Malia?
You know where you stole it from? Me.
For the kid, any truly stressful situation runs the risk of triggering this fully developed Spark.
Since this malformation is the closest to the werewolf,
it is more stable than either the kanima or the werejaguar in that
they can pass the abilities to children and propagate themselves as a separate species.
But the flaw here is the key to recognizing them as malformed.
Looking at the windigo we have only a little information to go on.
They can apparently reproduce sexually and so have become a
recognized subspecies within this universe.
But they have a huge and obvious flaw.
Sean: I'm so hungry.
I'm just so hungry!
Their insane appetite can cause them to lose all control.
The life of the average wendigo would be a constant hunt for food
just so they can maintain a somewhat normal life.
Patrick: Open you eyes.
Calissa! Open your eyes!
This need to feed is why Sean's family had that big freezer full of corpses
because, if they don't keep their kids fed, they'll turn feral.
That is a huge flaw and it says to me that wendigo are just another malformation.
The Löwenmensch is, I believe,
the best malformation and unfortunately the one we know the least about.
It's impossible to know exactly what the lion malformation might have been like because,
by the time we meet Douglas in World War II, he's already killed an alpha werewolf
and going from löwenmensch to regular werewolf with leftover lion traits.
So we don't know what Douglas the little lion man looked like or what flaws he might have had.
I'm only certain that he was a malformation because his seems to be a similar path to
that we saw with Jackson - from full kanima to werewolf with leftover kanima traits.
I mean, I can guess why Douglas's soul was so
twisted as to turn the bite into something malformed.
And the lion thing might have been caused by the unearned
pride and delusional superiority that was fostered by Douglas's culture at the time.
But we don't know enough to pin him with a specific malformed flaw.