kk, well exar kun also didnt demonstrate lightning yet the dark side source book claimed he mastered it, and force shield is a basic ability
well i dont know if he said 2 times of sidious or 2x of himself, sidious is hell powerful you know especially by DE but i believe its only because he learnt more techniques,
well even if its 2x of sidious then NJO luke would be 2.1 to 2.2 times stronger than vader, because lucas exact quote is
"as anakin skywalker, darth vader is roughly 80% of sidious, had he not sustained his injuries he would have been twice as powerful,"
well yes i think twice as powerful as sidious but isnt vader stronger than anakin? because lucas said as anakin skywalker and OT vader has demonstrated some incredible abilities like choking his officer while looking at him on the tv screen? thats quite a distance away considering the size of the executor and also vader due to experience is stronger than anakin
vader by the OT could have been even 90% or maybe even 95% of the emperor but not as powerful due to that he cant use lightning
thats my opinion because the 80% thing when lucas mentioned was as anakin skywalker, not OT vader
doesnt it make a little bit of sense? its a 19 year gap