This is going to be difficult. A Lewis base is an electron pair donator. A reducing agent is essentially an electron acceptor. Silver (I) oxide is about the best thing I can think of at the moment.

BTW K2O is not considered an oxidising agent at all in any standard chemical environment.

$\ce{FeO4^2-}$ ?

I guess I figured in the world of inorganic chemistry there isn't any, but what about in the world of organic chemistry? Ironically, I only know of 1 example the other-way-around. The other way around is, something that is a strong acid and a strong oxidizer? So the only example I have for that being HI.

@Poutnik Those high oxidation state transition metal acids tend to be pretty strong - but you may be right, who know what the pKa of Ferric acid is?

@IanBush I guess pKa measurement can be a bit of problem, because ferrates are stable AFAIK only in strongly alkalic pH.

@Poutnik Exactamundo. Similarly for high oxidation state xenon-oxygen compounds.

Alkali metal peroxides come to mind. (Not so much the alkaline earth metal counterparts, whose basicity is limited by low solubility in water.)

$\ce{KO2}$ will do.

My guess is that due higher electronegativity, Oxo acids of xenon would be stronger and conjugate base weaker.

Hypochlorite is a possibility

@IanBush so is AgO2 a stronger oxidizer than CaO, MgO, Li2O, Na2O, and K2O?

Note it is Ag2O. And yes, very much so - silver (1) is very easily reduced to silver metal (e.g. en.wikipedia.org/wiki/Tollens%27_reagent) whereas all the alkali and alkaline earth metals are very difficult to extract from their compounds. Consider, silver has been known since pre-history, while metallic sodium was only first isolated in 1807

@IanBush and as for "hypochlorite is a possibility" I believe HClO4is stronger acid and oxifider than HClO3 and HClO. NaOCl is a weak oxidizer but neither acidic nor basic. Only reason bleach's pH is in the 12-13 range is not cuz of the 10% NaOCl, but the 1% NaOH.

HOCl is a weak acid (pka ~7.5, so about a 1000 times weaker than vinegar). Therefore OCl- is a comparatively good base and NaOCl will have a pH somewhat above 7 in water. And according to en.wikipedia.org/wiki/Standard_electrode_potential_(data_pag‌​e) the standard electrode potential for HOCl is larger than either HOCl3 or HOCl4. Remember you can use bleach to oxidise Fe(II) to Fe(VI) (see en.wikipedia.org/wiki/Ferrate(VI))

@IanBush wow so the order is HClO > HClO4 > HClO2 > HClO3?

Of course, primarily because of solubility. Dissolution is considered oart of the dissociation process that makes a base (or acid) strong.

Oh, so THAT'S why my intended answer is now the foil for a comment explosion. @andselisk how would you suggest improving it?

How is this question not focused?

Not sure why this question needed more focus. It was focused enough for me to provide a simple answer, which was unfortunately reduced to a comment. Voted to reopen.

@EdV is there an objective truth that Mg metal is more reactive than Zn metal? For example, you say Mn reacts with H2 more than Zn, but couldn't Zn react with something else more than Mg reacts with something else?

@Oscar I also VTO'd.

@EdV sorry, but I can't post comments in other threads. I don't have enough rep. But thank for you answering my question that reactivity in metals is objective. I always wondered if 1 metal is objectively more reactive to acids, then it must be so for something like bases too.

@EdV yea hot concentrated nitric acid does not dissolve Al or Cr. Ag generally does not react with non-oxidizing acids, and reacts with oxidizing acids, but an exception is with HI. Ag reacts with HI, and HI is a reducing-acid. Your example with Al and NaOH is weird, as most bases do dissolve Al, so nothing new there.

@EdV since you're an Emeritus, and I'm banned from posting new Qs, I thought I'd hijack you here. On the history of chemiluminescence. Wikipedia page says the 1st chemiluminescence was discovered in 1877. But the source is in German language. Is there anything that keeps track of all the chemiluminescence discoveries? I'm curious to know what was the 1st chemiluminescence discovered by theory, and not by accident. And what about in the past 20 years, are they still being discovered by accident or by theory?

@Poutnik so why is this thread closed? What is to teach me?

You should ask the voters for the closure. About learning, try How do I ask a good question.

@ToddMinehardt can you answer my other question here?

@NealConroy No, it's against the rules. Please refrain from asking until your ban is lifted.

@ToddMinehardt I don't know about that, I doubt the rules would apply to you, but in any event, I hope today's incident will not increase my ban length.

The ban is system imposed, so we can't do anything about it. For what it's worth, a one-line question like this is not likely to get a good response on Stack Exchange. If you find that your question isn't worth writing more than one line about, then it's not really going to inspire answers that are more than one line; and if that's what you care about, then you already got one-line answers in the comments. [...]

[...] Before you mention the stuff you edited out from your question: what you wrote there is just not right (K2O is not oxidising at all), and you never actually gave us any insight into why you thought that was the case, so what are we supposed to say beyond "no it's not"? If you want to ask one liner questions, then I'd suggest trying a more open / less focused community, like Reddit or some other kind of online forum.