The Wall Brown (Lasiommata megera) looks very similar to the Large Wall Brown (Lasiommata maera) and the underside of the wings is indistinguishable from the underside of the Large Wall Brown. 
However, the upperside of the wings of the Large Wall Brown is mainly brown (especially the base of the wings) and have less orange markings than the Wall Brown.
In addition, the black eyespots on the top of the hindwing of the Large Wll Brown are not in an orange square-like area, but in an orange circle.

1st, 2nd & 3rd photo: Nature Reserve Hoge Venen, Luik, Belgium, 7 August 2022
4th & 5th photo: Viroin Hermeton Nature Park, Namur, Belgium 12 August 2024