Mixamo (now Adobe Mixamo) allows us to choose character and then animations from its website from free samples. I have done one simple animation and added the model to Unity. The animation works fine but the model is very changed once being imported, have a look here.
I am using following import settings,
Format: Fbx for Unity
Skin: With Skin
Keyframe Reduction: Uniform
I tried "Fbx" format only too, but no luck.I also applied "humanoid" in rigging, but I think it is not relevant here. Since I am not good with modeling that is why I am using this service, and I have no idea how to tackle this. Once it did worked well, but unfortunately I could not remember how, so I am stuck again.