He will go after his opponents, force them to spend a great deal of money on legal bills.
Be humiliated, reputation damaged, a target for crazy MAGAs, etc etc.

It is not the end result that Trump is interesting in, it is the legal process.
Legal warfare.

I won't link but the pieces are easy enough to find.

The Indictment Against Comey Should Be Dismissed

The vindictive indictment the Trump Justice Department barely managed to get a grand jury to approve on Thursday is so ill-conceived and incompetently drafted, he should be able to get it thrown out on a pretrial motion to dismiss. Legally, he’ll be entitled to that, and it would short-circuit the very expensive and punitive litigation process.

Yet, the case has been randomly assigned to a Biden-appointee in the Eastern District of Virginia, Judge Michael Nachmanoff. If Judge Nachmanoff throws the case out pretrial, President Trump and his supporters will rail that the fix was in. So as pointless as a trial would be, Comey and the court may want the vindication of a swift jury acquittal.

It’s a hard call. But it’s not a hard case. It’s a mess.

What’s Wrong with the Jim Comey Prosecution

There is really no doubt that the process was corrupted here. The Justice Department always answers to the president, but when the president is meddling directly in particular charging decisions and firing people who won’t bring charges against his political foes, that’s a very bad sign. It’s a much worse thing here: Trump has been openly calling for retribution going back to the campaign, and Trump isn’t a lawyer and obviously doesn’t much care what his enemies are indicted for — the textbook case of “picking the man and then searching the law books, or putting investigators to work, to pin some offense on him.”

And if the jury acquits Comey, their names and addresses will be mysteriously leaked.

I know everyone says this is a weak case. I believe that is the overall point that Trump is going to hold over everyone. It doesn't matter if it's a shame case. He will bully and threaten until he gets a guilty verdict.

I posted a few days ago that this case will blow up in his face. I've since realized it can't. Any acquittal will result in Trump saying that Democrats have ruined the justice system and that they shouldn't be allowed to serve on juries. And if he bullies and threatens his way to a conviction, the flood gates will open.