This is the 15009th most frequent German word.
schwächen
To weaken.
Here 'schwächen' is used as a verb, meaning to weaken or make weaker.
Die Krankheit kann das Immunsystem erheblich schwächen.
The illness can significantly weaken the immune system.
Here 'Schwächen' is the plural noun form, meaning shortcomings or flaws.
Die Schwächen des Plans wurden schnell offensichtlich.
The weaknesses of the plan quickly became apparent.
In this sentence, 'schwächen' is used figuratively to mean undermining or lessening the strength of something non-physical, like arguments.