26 languages, 46 bytes, Score : 1.68861953e-28 (0.000000000000000000000000000168861953)
All the languages are mainstream ones (i.e. they are actually used by people in development) and there's no REPL solution in any language. This answer is never going to win, but that's not a reason for not posting it...
//#**print()ale123456789+chous :f{}:""enttd *;
1. Python 2
print 1#//**()alechous:f{}:23456789+ ""enttd*;
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2. Python 3
print(2)#//**alechous13456789+: f{}: ""enttd*;
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3. Ruby
puts 3#//**()alecho:f12456789+{}rin: ""enttd*;
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4. CoffeeScript
alert 4#//**()pinchous:12356789+f{}: ""enttd*;
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5. PHP
echo 5/*alrt#()pinus:f{:12346789+} ""enttd;**/
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6. Perl 5
print 6#/*ale()chous:12345789+f{:} */""enttd*;
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7. Perl 6
print 7#/*ale)(chous:f12345689+{:} */""enttd*;
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8. JavaScript (ES5)
alert(8)//pin 12345679+#*chous:f{:} *""enttd*;
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9. JavaScript (ES6)
alert(9)//inp 12345678+#*chous: f{:}*""enttd*;
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10. JavaScript (ES7)
alert(9+1)//pni #*chous2345678: f{:}*""enttd*;
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11. Batch
echo 9+2 ::alrt()//pni#*usf{1345678}*""enttd*;
Couldn't find an online interpreter for this one. Try running this code in the Command Prompt, if you are on Windows.
12. Bash
echo 12 #::alrt(3456789+)//pni*usf{}*""enttd*;
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13. CSS
*:after{content:"13" /*h# l(2456789+)pisud;*/}
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14. Less
*:after{content:"14" /*#h l(2356789+)pisud;*/}
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15. Stylus
*:after{content:"15" /*#hl (2346789+)pisud;*/}
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16. TypeScript
alert(16)//inp #*chous2345789+: :{f}*""entt*d;
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17. Octave
disp(17)#//n *chou2345689+: :{f}*""entt*alert;
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18. Swift
print(18)//ds# *chou2345679+: :{f}""ent*ale*t;
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19. Julia
print(19)#ds// *chou2345678+: :{f}""ent*ale*t;
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20. Maxima
print(18+2);/*#ds ouch 345679::{f}""entale*t*/
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21. Clojure
(print "21");/*#ds ouch3456789+::{f}entale*t*/
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22. Groovy
print 19+3//();*#ds oh245678::{fuc*}entalet*""
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23. CommonLisp
(print 23);//*#ds oh1456789+::{fuc*}entalet*""
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24. EmacsLisp
(print 24);//*#ds oh1356789+::{fuc*}entalet*""
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25. PicoLisp
(print 25);//*#ds oh1346789+::{fuc*}entalet*""
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26. Logo
print 21+5 ;//*#dsoh346789::{fuc*}entalet*""()
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#
is the comment symbol in 5 languages, good solution would be1#2345
\$\endgroup\$