Hm, that requires some guessing since there a few of them that come to mind deserving that :D
Since you explicitely name him some thaughts on him and his abilities (having finished, this got more than I aimed for, sorry...):
Before going into detail just let me start by saying that I like him and the concept behind him a lot - he is one of the few characters that even on his own can be played quite strategic. On the other hand it means that be basically needs to played in certain ways to shine. Which admittedly he already can. I actually think at least in PvE he performs quite well after the last tunings. Even there are some problems, though, one certainly being that at least 3 of his abilities are basically never used. A bigger one might be that there is an Eddie for almost every situation that is better than him. Which is ok if that is intended and balanced but feels not only strange for a 5* but also given his (supposed?) role. This fact becomes severly more important in PvP.
Being overshadowed by other Eddies is most obvious when comparing him to Rainmaker I guess. The two are highly comparable and after Rainmaker got the abilities from VH that basically made him unique (mark and claim) one strongly feels compelled to do so.
Additional to that I think it is due to his rather unique way of playing with which the AI simply cannot keep up that he basically useless on PvP defence. I haven't tested him since the last AI tweaks, but the reliance of debuffs and buffs as well as a judgement about risk vs reward required are just too much. Since that is the core of that character I wouldn't change it, though - except for the luck element but I'll come to that. Most other Eddie's aren't made for defence either and that's ok.
So, let's talk abilities:
- Stake: The only power that is truly unique to him and there is nothing to complain here. It basically makes the character who he is at the moment. Marks on the target are a mere bonus on this ability, even without them the pure damage makes it worth using. Power costs are fair, the crit buff is just the icing on the cake.
- Claim: Might be my favourite ability of his. Not because it is the strongest (although it definetely is strong) but it is all around useful. For damage as well as for heal (the latter actually useful now). It requires either set up or thinking and it is quite interesting that it is a heal that can be countered in an unsual way.
This is a time to stop and point out: these are the only two abilities one will usually use (exceptions to be named later on).
- Mark: making our way down in usefulness we arrive at this interesting power. And it really is. I mentioned elsewhere that the initial damage calculation is weird at the moment, so depending how that is fixed that might chance its usability a lot (first candidate for the mentioned buff, yay!). As it is it is quite simple: If you get another turn it's great, if you don't it's really "meh" except for two cases: it obviously is great on high health targets that cannot be cleansed; otherwise it is needed to set up a heal in the following round. The latter case is quite restrictive because it again requires no cleanser and more importantly has to be used at the end of your turn because your allies will consume the mark (you can of course choose to not hit perfect which I actually do from time to time...). As I said, an "interesting" ability, mainly due to its synergies. If it becomes a "decent damage with a mark on top and chance for another turn" instead of a "mark with marginal damage" ability that wouldn't make the character too strong.
- Scream: we come to the first ability that basically no one, not even here, will know by name. I have to say, most of the time I use it I forgot I am in the past zone and click it accidentally. However, it is not as bad as that sounds. It certainly has a use in PvP where Immunity is of high value, but I am not sure if that is enough. I will test the fury gain again, but the buff is basically the only reason to use it. 20% chance of an extra turn (we require luck again. That's not only poison for PvP but will become a pattern for this character) is waaay to low in my opinion. I know it cannot be spamable or an automatic use every turn. And of course there are a lot of Eddie's who have highly situational and often questionable defensive powers of this kind (Hi there, Tailgunner and Aces High) but I have to wonder if that was intentional. All around this one could see a buff, but it doesn't hurt the way it is now.
Now we come to those that I wouldn't even notice if they were gone:
- Strike: If it hits crtitical and if the extra strike triggers it can do ok damage. But the chances of that happening... Especially when compared to Rainmaker this ability feels very lackluster (yeah, not easiest benchmark to reach, but again: the similarity of the characters provoke this). RttH shows that this ability can actually do damage, but of course there is not much left of it when only half of the relevant attributes of a character are taken into account for its damage. It is usually not the biggsest problem because, as stated above there are enough alternatives to it, but even as basic ability this one is neither fun or helpful (usual logic: are there multiple enemies?->use claim, do you have power?->use stake, with some cases overlapping where you have an option). The main problem with this might be that the damage when taunted can be extremely low (no class advantage against sentinels doesn't help), which is really strange for an usual high hitter. All in all we have a second contender for the buff worthy ability.
- Rouse: To me this ability is honesty completely useless in its current form. The damage is kinda ok, but if we wanted damage we would use stake. At the heart of this ability is of course the revive, which is supposed to justify its power cost. Well, it doesn't. Mainly because it's not a revive, it is the small chance of a revive. 35% are just a joke (good luck by the way coming up with an accuracy buff at the stage of a battle where the ability is needed). Seriously, if the chance was increased to 100% - take away the damage if you have - it wouldn't be too strong. I know it is hard to compare abilities from different chars because of the roles they play but when Pharao's has a 100% chance for all (!) characers with an extra heal, the rescuer's has 100% chance for all (!) characters with one of the strongest buff in the game this just is way off. One character is fine, but the gamble is basically never worth taking. Even at zero power cost you would still sacrifice either a huge amount of damage or some certainly highly needed heal (because you are in a situation where an ally is already dead that is guaranteed). So even then I would not use it, just to get a 65% of nothing worthwhile happening. So if I had to chose I would definitly chose this one for an overhaul and your wording of "making it stronger" gives me some hope, since it is not implying purely increasing damage.
Some concluding remarks: Luck is way to prevelant to make him useful in PvP. Marks are also needed for an efficient use and are hard to set up by VH himself (mostly, of course, again due to chances and luck). Both of these facts make the Warrior Bomber Boy a great addition to him and, in my mind, bring him to the level he should be without him. While I love the fact that there is a great synergy between them that of course makes everything regarding balancing much more complicated. If you tune him to be great without accuracy buffs and a mark supplier he will likely be overpowered with one in your team. If you tune him to be great with one in your team you risk of him being highly limited in its usefulness due to a static team composition and basically unlucky people (yay, we are coming back to this one on a whole new level) who doesn't have the BB over similar toons (and now you will need two, because just a troll for the passive is not enough) are ... well, not to go into profanity: unlucky. It is no coincidence that his decent abilities are the ones not depending on chance.
So my first step would be to make the element of chance much less important and a flat revive and an overhaul of Strike (you showed in the case of Rainmaker that you are not afraid of exchanging abilities, so I have some hope) would be a good to that. I guess I would still keep the BB around but the dependance on him would greately decrease.
Well, this became more than I thought. Would have put it into his thread, but here will do I guess.
(Since it really got more than expected I am sorry for any spelling mistakes, I don't have the concentration to read through everything again, I hope it doesn't hinder understanding at any point...)