I'd choose the venerable
Ulaire Enquea, Lieutenant of Morgul. Love the design for this one:
- Defensive use (and easily splashed) against large fellowships.
- Offensive use by designing a deck to get to 5 burdens.
- Directly kills companions of your choosing, which is as satisfying as it gets.
- Can still be countered by decks prepared for him (e.g. with maneuver wounding).
Wish it was legal in Standard.