Killing Arthur Wellesley at any point helps the French but
Working on a timeline in my head where part of it involves killing off Wellington during the Peninsular War. I've read somewhere that El Bodon was a good opportunity for the French. Are there any better options?
The idea is that killing off Wellington doesn't make Napoleon win, just delays a British victory for a few more years.
El Bodon in September 1811 is too late, even if all you are hoping is a few more months for Napoleon.
By that time Wellington has cleared Portugal, defeating the French on decisively three separate occasions and holding them in two more major battles, besides many minor engagements .
In addition he arranged for the Portuguese army to be trained to a point where they were better than most of the French in Spain.
At that point the British would not simply abandon Portugal and there was no way that French could simply bull through the Lines of Torres Vedras to Lisbon.
Remember Napoleon had already dispersed his forces trying to hold the whole Spain. This left them vulnerable to the spanish partisans and to defeat in detail (See the Battle of Barossa in Spring 1811)
In Europe as a whole, the continental powers knew that Napoleon was fallible & everyone (including the French) were completely ignoring Napoleons orders not to trade with Britain. Though Austria and Prussia were still cowed, Russia had simply stopped doing what Napoleon demanded.
By September 1811, whatever was happening in Spain, Napoleon had no choice but to take one of the "Many Roads to Moscow" in 1812 ... and everyone of those was a road to ruin.
Now if Arthur were to die in India, say when his horse was piked at Assaye, that might be different....