The Ta 152 or the Ta 183.
The Ta 152 was barely able to get out of its own way at 48,000 feet. An excellent aircraft at 41K, it was quite literally at the end of its tether at 48K
The Ta-183 was a pipe dream, nothing more, nothing less. While there are lots of comments on how much the MiG-15 resembled in the popular media, the resemblance is a matter of form/function not duplication. The U.S. F-86 also bears a striking resemblance even though you can clearly trace the Sable through its immediate predecessor, the straight winged FJ-1 Fury, again a matter of form/function.
The Saber, of course has a large number of difference from the MiG and both have a huge difference from the Ta-183: They could ACTUALLY FLY. The Ta-183, simply put, would never have flown, NEVER.
Next time you look at a MiG-15 (or its cousins the -17 &-19) you will notice that the Soviet engineers messed up the beautiful lines of the Ta-183 (assuming the bird was in fact inspired by the Reich design) with metal "fences" on the wings. Those fences are there for one reason only, the damned aircraft will not maintain stable flight without them. Stable flight is very important, at least to designers building things without a Nazi emblem on them (the Ho-229, along with the Ta-183, demonstrate that the Luftwaffe designers were not as concerned with stability as with a pretty design that would keep them out of the Heer).
The B-36 was also a POS, but it would not have been the critical aircraft, that would have been 1. The B-47, 2. The B-52, and, most importantly (& surprisingly to the casual observer) 3. The F-84G. The F-84G was, in many ways, a manned nuclear armed cruise missile, small, extremely fast, and almost impossible to intercept.
To address some of the other items that have been brought up
1. Could the Allies get air superiority over Europe?
Of course they could. By mid-1944 somewhere on the order of 85% of all German fighter production was being kept in the West. The Allies wiped them off the map in a brutal war of attrition. The American factories would not suddenly stop producing because the Soviets fell (might knock back the production numbers for the P-39 a bit).
All of Germany and Central Europe will be within bombing range of the Allies with the B-29, and with the F8B they will have a very fast extremely long ranged (430+mph & 2,800+ miles), piston engined escort aircraft aircraft to defend them all the way in & out.
2. Could the Allies outproduce the Reich?
Certainly. The BRITISH outproduced the Reich. The Reich will not be able to simply add the production of OTL USSR to that of Speer's slave works. Far too much of the Soviet production was dependent on both raw materials (frex: 2.3 million TONS of steel, 229,000 tons of aluminum, 103,000 tons of toluene) as well as completed items and prefabbed parts (frex: 350,000
trucks, 1.9 MILLION shell casings, 600,000 KILOMETERS of telephone wire) for the Reich to simply blink and turn Soviet manufacturing miracles into Nazi ones. Even Soviet oil production was greatly aided by both Western drilling equipment and by supplies of additive chemicals for the raw crude. This, of course does not even begin to factor in the 10,000 or so fighters and bombers, 6,000 tanks, 51,000 jeeps, etc. that allowed the Soviets to build more of their own equipment while doing the heavy lifting against the Reich.
3. Is the victorious Reich still resource poor?
Obviously. The vast majority of the USSR's mineral wealth is in the vastness of Siberia e.g. the East side of the Urals. That material is still outside of German control, and a defeated USSR is not going to be any better at pulling it out of the ground than the undefeated one was (it will just be short a few thousand locomotives and couple hundred thousand trucks to move whatever it does manage to get out of the ground). The Reich still has no access to natural rubber and ALL of its synthetic plants (including those in the General Government area) are well within bomber range from the UK, North Africa, and Iceland (folks seem to forget that the Allies have Iceland available to base/stage heavy & super-heavy bombers and long range fighters which is well out of the range of the Luftwaffe's striking arm).
The Reich has no hope of defeating the RN/USN, no hope of even challenging for control of the Sea lanes, and virtually no hope of breaking the Allied blockade.
4. Nazi wonder weapons
The only wonder part of the V-weapons is why anyone wonders about them. The V-1 was a failure, the V-2 was too short ranged to be a true threat and too damned hard to hide (all you need are a dozen or so radar tracks of the inbounds from three radar receivers and bang, the launch site is well known, followed shortly by being hit by a 1,000 plane raid), and the V-3 was a dumb joke.
The Me-262 was inferior to the Meteor AND the P-80, with follow on Allied designs far better, more reliable, and many built 3,000 miles outside of Goring's wildest dream for bombing range.
The late Nazi subs had some good, even excellent, features, but they were also still vulnerable to attack by the increasingly effective Allied ASW forces, which also had made huge technological strides, except the Allied strides tend to be ignored since they are not "wonder weapons.
As far as the Nazi fascination with huge land forts, I would say that the Allies would have supplied lunch for the work crews if the idiot Nazis would have actually tried to build the P.1000 Ratte (and would have thrown in supper if they had built the P.1500 Monster). If you can hit (and sink) a 37 meter wide battleship traveling at better than 30 MPH how much trouble does anyone thing it would be to hit a 13 meter wide tank moving at 10 mph? Stupidity squared.
The real question is IF the Allies would be willing to pay the price to defeat a Greater Germany. My guess is yes, but it isn't a total slam dunk.