Question

What is the strongest knot from leader line to hook?

Answer 1

The strongest knot is one that you can tie correctly in less than perfect conditions.  Low light, wind, rain or getting bounced around.  I personally use the San Diego Jam Knot and have never had any issues.
Proknot.com makes a credit card sized laminated knot guide for both fresh and saltwater knots.

Answer 2

I personally like he palomar knot. I think the knot strength is really good and it is fairly easy to do. If I were given good conditions, I could probably do it in 20 seconds. Obviously if you're using fluro you won't retain more than 70% of your line strength even with a perfect knot. But I think this knot has held up for me and I haven't had any break offs yet. It works especially well with hooks and any sort of terminal tackle.

Answer 3

If you're not considering threading mono into hollow core braid then the SD Jam Knot.  YouTube Royal Polaris SD Jam Knot for a comprehensive video on how and why to ties this.  Good luck.