This is the 2800th most frequent German word.
rechtsextremen
"Rechtsextremen" means "far-right extremists" in English.
Here, 'rechtsextremen' is an adjective describing 'Gruppen' to indicate that they are affiliated with far-right ideologies.
Die Polizei beobachtet die Aktivitäten der rechtsextremen Gruppen.
The police monitor the activities of the far-right groups.
'Rechtsextreme' is used as an adjective modifying 'Aktivitäten,' describing them as being associated with far-right extremism.
Es gab Berichte über rechtsextreme Aktivitäten in der Stadt.
There were reports of far-right activities in the city.
In this case, 'rechtsextremen' modifies 'Teilnehmern,' identifying the participants as those with far-right associations.