Let me rephrase...My only resort is to go vertical and the bad guy is going to follow.
If this is the case something has already gone terribly wrong and any situation where you can what if it all day is hard to explain how to beat it.
So you have a Spit 9(type fighter) 1K behind your K4....you have E and they manuever ed to get there on your 6 (this is the situation I'm reading from your posts)...
If they maneuvered to get there and have less E then you...a zoom climb to get above your opponent is easy. You base your pitch not off a standard say like 45 degrees but off what your opponent decides to do with his pitch. If they match your pitch, make yours steeper, if they shallow out to keep energy you can shallows yours....I would also suggest adding a spiral into it to force them to lose that energy to follow you...in a spiral climb your objective is to create an angle where they flip their plane over to follow your spiral....this is where they burn the most energy because gravity and lift are both pointed toward the earth.
If the plane is closing on you....going vertical is the best way to close the energy gap between you and your opponent. A lot of people preach the split s but you are just giving up the fight over and over...yea it's safe but it's going to end poorly.
You use a vertical manuever to force an overshoot. Going vertical in a reverse is risky but if done correctly leads to better position to force a rolling scissors or vertical scissor or even to gain a shot opportunity as the enemy flys by. You do this by starting a turn creating an obtuse angle between their nose and your wingtip. As they get closer you tigthen that turn to create a 90 degree angle from your fuselage and their nose...at this point just before they have guns you go vertical into a barrel roll as the over shoot you try to keep your roll behind their 3 9 line (their wings) kinda like you would in a turn fight...
These are hard to type about, I do feel like the community deserves a good video explanation because a lot of players struggle against this.