-- Module: Mathlib.AlgebraicGeometry.Group.Abelian
Goal:
K : Type u
inst : Field K
inst_1 : IsAlgClosed K
G : Over (Spec (CommRingCat.of K))
inst_2 : IsProper G.hom
inst_3 : IsIntegral.{u} (tensorObj (𝒞 := instCategoryOver) G G).left
inst_4 : GrpObj G
S : Scheme := Spec (CommRingCat.of K)
point : ↥S := IsLocalRing.closedPoint K
hpoint : IsClosed (X := ↥S) {point}
this_1 : Nonempty.{u + 1} ↥G.left
this_2 : IsProper (tensorObj (𝒞 := instCategoryOver) G G).hom
this_3 : JacobsonSpace.{u} ↥(tensorObj (𝒞 := instCategoryOver) G G).left
this_4 : Surjective G.hom
this_5 : IsProper (X := (tensorObj (𝒞 := instCategoryOver) G G).left) (Over.Hom.left (fst G G))
this_6 : Surjective (X := (tensorObj (𝒞 := instCategoryOver) G G).left) (Over.Hom.left (fst G G))
this_7 : IsProper (X := (tensorObj (𝒞 := instCategoryOver) G G).left) (Over.Hom.left (GrpObj.commutator G) ≫ G.hom)
this_8 :
  IsClosedImmersion (X :=
    Over.left (X := Spec (CommRingCat.of K)) ((𝟙_ (Over (Spec (CommRingCat.of K)))) (𝒞 := instCategoryOver)))
    (Over.Hom.left (lift η η) ≫ Over.Hom.left (fst G G))
this_9 :
  IsClosedImmersion.{u} (X :=
    Over.left (X := Spec (CommRingCat.of K)) ((𝟙_ (Over (Spec (CommRingCat.of K)))) (𝒞 := instCategoryOver))) (Y :=
    (tensorObj (𝒞 := instCategoryOver) G G).left) (Over.Hom.left (lift η η))
γ : tensorObj (𝒞 := instCategoryOver) G G ⟶ tensorObj (𝒞 := instCategoryOver) G G :=
  lift (fst G G) (GrpObj.commutator G)
this_10 : IsProper (Over.Hom.left γ ≫ Over.Hom.left (fst G G))
this : IsProper (Over.Hom.left γ)
H :
  Set.Nonempty (α := ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
    (Set.preimage (β := ↥G.left) (⇑(Over.Hom.left (fst G G)))
        (singleton (α := ↥G.left) ((Over.Hom.left η) point : ↥G.left)) \
      Set.preimage (β := ↥(tensorObj (𝒞 := instCategoryOver) G G).left) (⇑(Over.Hom.left γ))
        (singleton (α := ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
          ((Over.Hom.left (lift η η)) point : ↥(tensorObj (𝒞 := instCategoryOver) G G).left)))
obtain :
  ∀ (c₀ : ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
    (hc₃ :
      Membership.mem (γ := Set ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
        (closedPoints ↥(tensorObj (𝒞 := instCategoryOver) G G).left) c₀)
    (hc₁ :
      Membership.mem (γ := Set ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
        (Set.preimage (β := ↥G.left) (⇑(Over.Hom.left (fst G G)))
          (singleton (α := ↥G.left) ((Over.Hom.left η) point : ↥G.left)))
        c₀)
    (hc₂ :
      c₀ ∉
        Set.preimage (β := ↥(tensorObj (𝒞 := instCategoryOver) G G).left) (⇑(Over.Hom.left γ))
          (singleton (α := ↥(tensorObj (𝒞 := instCategoryOver) G G).left)
            ((Over.Hom.left (lift η η)) point : ↥(tensorObj (𝒞 := instCategoryOver) G G).left))),
    False
⊢ False

Tactic:
obtain ⟨c₀, ⟨hc₁, hc₂⟩, hc₃⟩ := nonempty_inter_closedPoints H <| by
      rw [Set.diff_eq_compl_inter, ← Set.image_singleton, ← Set.image_singleton];
      refine (IsOpen.isLocallyClosed ?_).inter (IsClosed.isLocallyClosed ?_)
      · exact (((lift η[G] η[G]).left.isClosedMap _ hpoint).preimage γ.left.continuous).isOpen_compl
      · exact (η[G].left.isClosedMap _ hpoint).preimage (fst G G).left.continuous

Premises used: nonempty_inter_closedPoints