List of various terms of endearment that can be used in different languages. A lot of them are gender neutral.
Habibi ŲŲØŁŲØŁ (m) (my love)
Ya hayati ŁŲ§ ŲŁŲ§ŲŖŁ (my life)
Ya qalbi ŁŲ§ ŁŁŲØŁ (my heart)
Ya ruhi ŁŲ§ Ų±ŁŲŁ (my soul)
Hubbi/hobbi ŲŲØŁ (my love)
Liebling (beloved/favourite)
Schatz (treasure, I would say the most common one between established couples)
Liebes (loved one) (f, I don't find it that romantic)
Liebster (m) (loved one, bit old-fashioned)
Liebste (f) (loved one, bit old-fashioned)
Engel / Engelchen (angel)
Prinzessin (f) (princess)
Kleines (f) (little one, can be used in a cute way for women, but can also sound degrading or offensive)
ChƩri (m) / ChƩrie (f) (darling)
Chou (used like "honey", but directly translates to cabbage)
Cucciola (puppy/cub) (mostly used for women, but you could say "cucciolo" for men)
Piccola (little one) (mostly for women, "piccolo" would be the male version)
Cara/caro (dear) (now mostly used by grandmas for grandkids but perfect for couples in the past or old couples nowadays
Patata/patatina (potato/little potato) (again mostly women when used romantically, "patato/patatino" for men, but they can also be used for pets, babies, your kids or anyone that you find cute)
Tata/tato (short version of papata/patato)
Polpetta/polpettina (meatball/little meatball) (very uncommon, but I've heard it used for girls)
Topolina (little mouse) (very uncommon, but could be used for girls)
Iubi (Sweet heart/darling)
Draga mea (f) / Dragul meu (m) (my dear)
DulceaČa mea (jam/honey)
KocacıÄım/karıcıÄım
(my husband/my wife, but in a more endearing way, you can say it to a person you're not married yet but thinking about marrying)
Her Åeyim (my everything)
YaÅama sebebim (my reason to live)
Ceylanım (My gazelle, it's a gorgeous creature like cmon)
Güzel gözlüm (My lover with beautiful eyes)
Nazlı yarim (My coy lover)
Kalbimin sahibi (the owner of my heart)
Güzelim/yakıÅıklım (my beautiful/my handsome)
KediciÄim (my kitty/kitten)
BiriciÄim/bi'tanem (my one and only)
Balım (my honey) (can also say "bal dudaklım (my lover with honey lips)" if you feeling on fire)
Evimin direÄi (literally meaning "the post of my house," if you say this to a person (usually your husband), you mean to say that he keeps your household/family up, whether financially or with emotional maturity)
Chaim sheli ×××× ×©×× (my life)
Neshama sheli × ×©×× ×©×× (my soul)
Lev sheli ×× ×©×× (my heart)
Meri jaan ą¤®ą„ą¤°ą„ ą¤ą¤¾ą¤Ø (f) (my life)
Mera jaan (m/n) (my life)
Rani ą¤°ą¤¾ą¤Øą„ (f) (queen)
Azizam Ų¹Ų²ŪŲ²Ł
Ā (my dear)
Asalam Ų¹Ų³ŁŁ
(my honey)
Meri jaan Ł
ŪŲ±Ū Ų¬Ų§Ł (my life)
Pyaari پŪŲ§Ų±Ū (sweetheart)
Shahzadi Ų“ŪŲ²Ų§ŲÆŪ (f) (princess)
Myszko (f) (little mouse for women romantic, or for young daughters)
Misiu (m) (diminutive bear, romantic for men)
Misiaczku (another form of the above but more intersex)
SÅoneczko (diminutive for sun, can be for children but also romantic for women)
PÄ
czusiu (diminutive doughnut, romantic partner)
BÄ
belku (bubble diminutive for young children, toddlers or infants)
Duszko moja (very outdated, meaning my soul, for women)
Serce moje (also old school, meaning my heart, unisex)
Gwiazdeczko (diminutive star, for girls and romantic female partner)
Kotek/Kotku (kitten, unisex)
MaÅa (literally: little (f), for women, can be romantic but also offensive if used by strangers)
skarbie (my treasure, unisex)
rybciu (diminutive for fish, little fish, for women)
żabko (diminutive for frog, little frog, for women)
Jagiya ģźø°ģ¼Ā (honey/baby)
Aegiya ģ źø°ģ¼ (baby/little one)
Gongjunim 공주ėĀ (f) (princess)
Wangjanim ģģėĀ (m) (prince)
Nae Sarang ė“ ģ¬ėĀ (my love)
Gwiyomi ź·ģ미 (cutie)
Zlato (gold, my precious)
MilĆ”Äku (dearest, little dear)
lyubov' moya / Š»ŃŠ±Š¾Š²Ń Š¼Š¾Ń (my love)
radost' moya / ŃŠ°Š“оŃŃŃ Š¼Š¾Ń (joy of mine)
dusha moya / Š“ŃŃŠ° Š¼Š¾Ń (my soul)
schast'e moyo / ŃŃŠ°ŃŃŃŠµ Š¼Š¾Ń (my happiness)
sokrovishche moyo / ŃŠ¾ŠŗŃŠ¾Š²ŠøŃŠµ Š¼Š¾Ń (my treasure)
solnyshko / ŃŠ¾Š»Š½ŃŃŠŗŠ¾ (sunny)
zolotce / золоŃŃŠµ (golden)
lyubimyj (m) + lyubimaya (f) / Š»ŃŠ±ŠøŠ¼Ńй + Š»ŃŠ±ŠøŠ¼Š°Ń (beloved)
dorogoj (m) + dorogaya (f) / Š“Š¾ŃŠ¾Š³Š¾Š¹ + Š“Š¾ŃŠ¾Š³Š°Ń (darling, dear)
milyj (m) + milaya (f) / Š¼ŠøŠ»ŃŠ¹ + Š¼ŠøŠ»Š°Ń (dear but in more informal way)
kotik / ŠŗŠ¾ŃŠøŠŗ (kitty) malysh / малŃŃ (baby)
zajchik (m) + zajka (f) / Š·Š°Š¹ŃŠøŠŗ + зайка (bunny)
ptenchik / ŠæŃŠµŠ½ŃŠøŠŗ (little bird, hatchling)
rybka moya (f) / ŃŃŠ±ŠŗŠ° Š¼Š¾Ń (my fish)
Meu querido (m)/ minha querida (f) (my darling)
Meu docinho (my sweetheart)
Amado (m)/Amada (f) (my love)
Meu (m)/ minha (f) mais que tudo (my above overall) Meu tesouro (my treasure)
Meu bem/ meu benzinho (my goodness)
Meu doce/meu docinho (my sweet/ my little sweet)
Querido (m) / Querida (f) (darling)
Meu bem (untraslatable; something between "my dear" and "my treasure")
Meu docinho de coco (my coconut candy - really old slang, nowadays used only for fun)
Patroa (f) (it means a female boss; not ironic not aggressive, but used by men to describe their wives affectionately, eg. "I can't go today, my patroa is waiting for me at home")
Gato/gatinho (m) / gata/gatinha (f) (cat/little cat; if a person is pretty, they are called a "cat")
Lindinha (beautiful/cutie)
Filipino (from various local languages, all gender neutral)
Mahal, sinta (tagalog) (love)
alternatively add "ko" or "aking" to turn it into "my love" (e.g. mahal ko, sinta ko; aking mahal, aking sinta) with "aking" being used more often when talking about the one you love to a 3rd party;
or turn it into a verb (e.g. aking minamahal, kasintahan) to make it "lover"
Paraluman, irog, liyag, giliw (tagalog) (darling) these are older terms though, you won't hear or see them being used unless you're lovers with someone šExtraš
Tangi (tagalog) (only one)
Tinatangi (tagalog) (the one i hold dear/the only one for me)
Tinadhana - fated (from the root word "tadhana" meaning fate, which in and of itself should also be a term of endearment and I stand by that)
Hinigugma (bisaya) (beloved) (very old)
Palangga/pangga/langga or "ga" for short and sometimes pagingging (ilonggo) (love) (can also be used platonically or between family members)
Kalasahan (tausug) (beloved) (this is pronounced with an emphasis in the SA syllable (as in kalaSAhan) instead of the LA like in the tagalog word LAsa (which means taste)
Jowa (filipino slang) (significant other/boyfriend/girlfriend)
Bebe, bebe ko, beh, bhe, bhie, bih (filipino slang) (babe)
Lablabs (filipino slang) (literally "love-love" in a heavy filipino accent)
MilĆ”Äik (bit cheesy, but means my lovely)
Sayang (to love/love, can be used as 'honey', doesn't have to be romantic)
Cintaku (my love, mostly used romantically)
ĪγάĻĪ· /ĪγάĻĪ· μοĻ
(love /my love) (the first can also be used among friends, usually between women, but both are very often used in romantic relationships)
ĪØĻ
ĻĪ® μοĻ
(my soul) (mostly romantic but can be used by a parent to their kid)
Let me know more terms of endearment in your languages! And please correct me if I'm wrong somewhere.
Please note that they are not all romantic. You can ask in the replies, so a native speaker can answer if it's appropiate for the type of relationship you want your characters to have.