Most likely:

curlywas (https://github.com/exoticorn/curlywas) -- c-like but very low-level; seems very complete; rust impl; mit license; short but seemingly thorough docs?

wa (https://github.com/wa-lang/wa) -- go-like, not clear how high/low level it is, thorough docs, seems promising, agpl license, lots of mandarin in docs

virgil (https://github.com/titzer/virgil) -- ruby-like? gc; cant find license; last commit 3 hours ago; thorough docs but all in md files in repo

assemblyscript (https://github.com/AssemblyScript/assemblyscript) -- typescript-like; apache 2 license, minimal runtime with gc; implemented in js

walt (https://github.com/ballercat/walt) -- JavaScript-like made for wasm, 25 contributors! decent looking docs, might actually be usable! most commits 7 years ago but last commit 3 years ago though, mit license

onyx (https://wasmer.io/posts/onyxlang-powered-by-wasmer, https://github.com/onyx-lang/onyx) -- ocaml-like? recent activity, full docs, bsd license, not sure if it has lower level capabilities or how much the higher level features cost at runtime or build time

waforth (https://github.com/remko/waforth) -- forth for wasm! upside is that its forth, downside is that its forth; mit license; great docs; seemingly inefficient due to constant lookups?

Less likely:

thinscript (https://github.com/evanw/thinscript) -- js-like with macros; abandoned 9 years ago; not yet licensed

wase (https://github.com/area9innovation/wase) -- C-like syntax but still wasm-like, not super recent but not super old, only a few contributors, not sure how complete it is but its docs give a feeling of being mostly-complete, MIT license

wam (https://github.com/kanaka/wam) -- wasm macro preprocessor, just one guy, last commit 7 years ago, very few built in macros, mozilla license (???)

wah (https://github.com/tmcw/wah) -- wasm but with infix, doesn't seem extensible with macros, two contributors, last commit 8 years ago, eclipse license (???)

Honorable mentions:

mini-c (https://github.com/maierfelix/mini-c) -- C to wasm compiler, seemingly abandoned 8 years ago, not sure how complete it is

c4wa (https://github.com/kign/c4wa) -- c to wasm compiler, no activity in 3 years, no license, written in java