So far as I know from personal experience - people I have known before and after they attained 'power' - high position, high status, fame, influence etc - this generalisation is true: perhaps 100% true (although there may be exceptions that have slipped my mind).
The main corruption I have observed is pervasive, habitual, systematic dishonesty - with the self and with others.
Of course there is a confounding element; which is that those who seek power, who do-what-it-takes to attain power - are usually partly, or at least latently, corrupt already. And there is the factor that uncorrupt (and probably-incorruptible) people would be excluded from power - unless by some error they happened on it, when they would normally be purged from the institution. But there is not much doubt that the environment of power is itself rapidly and pervasively corrupt-ing.
I do not think that this was always the case - indeed I'm confident that it was not always the case. In my fields of professional activity - medicine, science and academic generally - there used to be (as recently a couple of generations ago) quite a lot of people who attained power and influence and who were not corrupt. Quite a few of these survived until 25 years ago; but now there are, well, none who have power. (Only a few, and all marginalised.)
(In the past - even a few politicians remained basically honest!)
One thing observation reveals is that mainstream modern people - secular people, materialists, atheists - who are known for alternative, off-beat, dissenting, cynical views; nowadays always sell-out; indeed, my impression is that they actually live in-order-to sell-out. They develop their alternative careers until they have made just enough of a nuisance that they are worth bribing to conform - and they grab the opportunity with both hands.
Hence all the 'red hot radicals', the edgy nonconformists, the avant garde, the socialists, the men/ women of-the-people... with knighthoods, peerages, awards, prizes, and Establishment pulpits.
And I have not the slightest doubt that if any of the current crop of non-Christian 'Right Wingers' or 'Libertarian's' or Free marketeers, or Nationalists in the public sphere ever get a sniff of power, they will sell-out so fast that the transitional phase will be invisible - especially when they are kept-on as pretend-conservatives or pseudo-reactionaries; as fake evidence of the broad minded tolerance of the modern Establishment.
What I am saying is that - here and now - power and integrity are incompatible; and possession of power is sufficient evidence of achieved-corruption; and desire for power is sufficient evidence of willing corruptibility.