Looking for some suggestions from the hive mind, what is the single most powerful, or more to the point, most difficult mech to fight against, baring the Super Heavies, per rules level (standard, advanced, experimental)?
Powerful is one thing. People have mentioned the Hellstar, or Tomahawk, or Pillager, or any of those big shooty 'Mechs.
Most difficult to fight against? Wulfen C.
First: It has a 10/15/10 speed backed up by Stealth Armor. You will only ever engage it on its terms, never the opposite.
Second: It has three TargComp'd ER Mediums. It can reliably force a PSR on its own.
Third: It has options. It can run (with Stealth on) and fire all ER Mediums for +9 heat - allowing it to escape at 9/14/10 speeds the next turn. Or, it can jump 10 (with Stealth off), fire all ER Mediums for +13 heat, just shy of that shutdown roll. Run away, repeat. With Stealth off, it can do running backstabs all day.
Fourth: It is
the posterchild of a 'Mech that completely and utterly breaks the BV system. My group has come to the conclusion that adding an extra 400 BV to its price to makes "fair".