Fuck me, if it was a similarly sized dog that was having a pop at a small child you'd all be baying for it to be put down on the spot!
@Peonperfect Speak to the owners, but I would do so in writing so hopefully, you get an answer in writing.
Ask them:
Are you aware your cat is attacking us as we leave, he is actively chasing us and swiping at us?
Would you consider neutering your cat so he is less likely to do this, less likely to wander, take risks and get into fights and less likely to get an infection?
What would you suggest we do to get him off our front step and away from us?'
If they know their cat is dangerous to members of the public, and they choose to do nothing about that and you/your child are subsequently injured (and yes cats can inflict some nasty wounds if they want to) then yes, legal action CAN be taken. The idea that cat owners are 100% immune to legal action due to the behaviour of their pets is wrong - but you do have to have some proof that they were aware of that dangerous behaviour.
For now I would spray the step with citrus as cats typically don't like that and possibly get some of the cat silhouette with reflective eyes things that you can place so he feels like there are cats staring right at him, that often puts them off sitting somewhere!