There's always there being 'have been, badly'
And for english insults, theres always 'pillock' 'wanker' 'tosser' 'bell-end' 'arsehole' (yanks don't spell it right, its 'arse hole' not 'ass hole'
Or 'chocolate starfish' as a reference to the above. Turdburglar. Nonce (rather severely offensive, its a prison term for paedophile and plenty people would kick your head in for such an accusation) Twat, twunt, toss pot, fuckweasel, arsebandit, 'spacker' (english take on 'spastic', offensive as it gets to spesh people, and used by neurotypical people it'll result in the application of severe maiming and pain if ever heard spoken by yours truly.) Sarcastic humor by spesh people I'll just about tolerate. But used as an invective, its about as offensive as you can get.
And a few of my own,
'gutterfuck' 'whorebegotten' 'perdition-spawned whoreson' 'mitotic catastrophe' 'a turd no anus would willingly shit' 'fuckweasel' 'disease made flesh' 'cockmongrel'