Outshined or outshone? [duplicate]

Either is acceptable. Both have a history of transitive use.

First, the Corpus of Contemporary American English has more results for outshone (91) than outshined (27). In both search results are several instances where they take direct objects and function as transitive verbs. For example:

Well, you have definitely outshined and outdone us all. ("Maggie Rodriguez^s senior prom in 1987, "The Early Show on CBS, May 9, 2008.)

"The pride he had in his family outshone the success he had in business, " his brother Frank said. ("No More Phantom Wedding Guest, No Beach or Tower-Top Proposals," New York Times, February 12, 2002.)

Second, dictionaries vary in what form they report. The Oxford English Dictionary ("outshine, v.") documents the past participle and past tense form as such:

Inflections: Past tense and past participle outshone;

Examples after the early 17th century only include outshone, not outshined. For example:

1987 R. Ingalis End of Trag. 184 She outshone the light-reflecting surfaces of nature.

1989 TV Extra (Brisbane) 30 Apr. 4/2 They even go so far as to hint that David outshone Faye when it came to acting.

Merriam-Webster ("outshone") is more equivocal, allowing for either outshone or outshined:

outshone \ˌau̇t-​ˈshōn, especially British -​ˈshän\ or outshined; outshining

And this example shows a transitive usage for outshone:

outshone most of the other films in quality

In other words, you're free to go with whichever one you think sounds better, or to pick whichever basis of evidence (frequency; a favorite dictionary or publication) you like.